Big Block Buick twin turbo

[Ergot]

Has anyone done this? There is a trend ( for those with the green ) amongst the Chevy clan involving big cubes and twin turbos. Ive heard of some of these pro touring cars ( like Chicane ) that are well over 1,000 horsepower with this setup. There are several 57 chevys with the big block dual hair dryer setup. ( Bob Reiger and Hayden Motorsports to name a few )

http://www.promodifieds.net/Photos/Reiger/HTML/

I dunno if you guys have seen the Chicane car anywhere ( we saw it at the last Autorama here in dallas ) but those custom turbo headers look SO friggin beautiful. On top of that the car itself is just gorgeous.

I just want to do something different. I wonder what kind of power this sort of setup would make coupled with a Trishield level four race engine. :Brow:

Suddenly it is possible that I could afford something like that so im doing a little virtual shopping.

[bobc455]

I'm aware of one guy on the board who is in the midst of this setup.

Once the new blocks come out, I think you'll see a lot more engines like this. I got a quote on doing it to my 455, $7,000 (I already have FI) including twin intercoolers, custom headers, etc. I think a turbo setup would be wicked cool, but a supercharger would be easier.

-Bob Cunningham

[alan]

I agree, supercharging is easier. :Smarty:

I guess I'm just hard-headed! :Dou:


http://www.thedinosaurgang.com/greencar.htm

[AZ-69 Skylark]

I'm looking forward to seeing forced induction Buick bigblocks. A centrifugal sc is easier, but turbos are better/more effecient. I think the fullsize Buicks would be best for turbos as they have more room in the engine bay. Me, I've changed my mind and decided to try a smallblock with twin turbos and fuel injection...it will be a while though.

[Ergot]

alan said:I agree, supercharging is easier. :Smarty:

I guess I'm just hard-headed! :Dou:


http://www.thedinosaurgang.com/greencar.htm

Oh my God that is a beautiful/amazing/wood inducing/eyeball grabbing work of technological mastery! Hail the Dinosaur Gang! You guys own my new favorite Buick. :D

I know some folks are touchy about their numbers but I'd *love* to know what kind of torque that bad beast puts out. Im thinking the 455 would be very happy with the extra airflow. Yeehaw!

What an amazing machine.

[Ergot]

bobc455 said:I'm aware of one guy on the board who is in the midst of this setup.

Once the new blocks come out, I think you'll see a lot more engines like this. I got a quote on doing it to my 455, $7,000 (I already have FI) including twin intercoolers, custom headers, etc. I think a turbo setup would be wicked cool, but a supercharger would be easier.

-Bob Cunningham

Allot more engines like that would be awesome. Watch out twin turbo G bodies! The big guys are coming for yah! lol

Of course we'll have to have an extra parachute or two on the back to stop after running those mid 6 and 7 second quarters. j/k :)

7k.. Buick stuff is expensive. Worth it though for certain. Though 2600 for the xs procharger kit is quite reasonable. Maybe two of those would be the way to go. Can a centrifugal be two staged?

hehe

[Mike T]

Dual centrifugals, its been done. But its REALLY unneeded!

:)

An associate of mine builds custom turbo setups for a living and on several occasions we have started to build them...usually followed by a why? and then a never mind.

Turbos are more efficient, no doubt, but the complexity and cost of such systems, plus the HEAT, just really outweighs most other considerations. Unless you just GOT to have 'em! Sometimes its hard to beat the wow factor.

Kinda like an Offenhauser with dual quads, the single four is probably gonna run better with less work, but it just doesn't look as cool.:cool:

Mike T
XS Performance
http://www.xsperformance.com

[AZ-69 Skylark]

Mike, I know for the exhaust manifolds you can get an internal ceramic coating so good at blocking heat loss, they're actually only warm to the touch! The fact that you can touch them at all is a huge improvement. I'm not sure how effective turbo housing heatshields or coatings are for heat reduction.

[Stg1Regal]

Allot more engines like that would be awesome. Watch out twin turbo G bodies! The big guys are coming for yah! lol

Of course we'll have to have an extra parachute or two on the back to stop after running those mid 6 and 7 second quarters. j/k

But what if it's a Twin Turbo Big Block Buick in those G-bodies?

That would be SWEEET!! :laugh: :bglasses: :TU:

[Ergot]

Mike T said:Dual centrifugals, its been done. But its REALLY unneeded!

:)

<edit>

Mike T
XS Performance
http://www.xsperformance.com

Yea, I'd have to agree in the end that its major overkill. Especially when a single large turbo can produce enough boost to blow the heads off. Probably true for centrifugals as well. Lol.

There is that wow factor to consider but the XS Performance ( .net ) kit has plenty of wow going on as well. Richs car is brutishly beautiful! The price is very competative as well. Be nice to see more Buicks competing in classes allowing power adders like that.

:)

[Ergot]

Stg1Regal said:But what if it's a Twin Turbo Big Block Buick in those G-bodies?

That would be SWEEET!! :laugh: :bglasses: :TU:

Oh hell yes! Sweet Regal by the way. A buddy of mine had an 86 Monte SS with a stroker 383 in it. Holy mother of flaming pearls that bitch was almost scary to ride in. I bet your regal rips some serious ass!

Your cardomain site is gonna be really helpfull to me here in about a month as im swapping a 430 into a 66 skylark.

My trans is a longtail 400 though so Im still screwed out of a driveshaft. Balls!!!

later

[Stg1Regal]

:Brow:

Thanks Jason on the compliment....

Yep it does get up and move fast, but got issues with it being a peg leg 8.5 GN rear wich leads to big "lack of" traction issues:laugh: .

When I turn up the wick on her , I hope to have a scary ride also, right now if your a passenger in it and I nail it, it is scary , I've managed to catch a few off gaurd!!:TU:

Good luck in your project, touch base with me on any questions ,I'll do my best to help or answer.

Later

[Ergot]

Your welcome Chris!

Oh man... posi, and some 10.5 inch meats and I bet the Regal will be squishin spines and causeing riders to soil themselves if you even *think* about hitting the pedal hard enough to open up the secondaries in that big ole carb.

Gawd I love the Big Block community.. The scope of thinking is soooooooo different than most other arenas. I mean.. You dont see people with Nissan 240's dropping big blocks in them. Although I must admit to having had our asses handed to us in a very built 78 z28 by an old Z with a small block chevy wedged in there.

Talk about a go-cart with an attitude.

Thanks for the luck, I'll need it for sure. Definately will keep an eye on your cardomain page to see what you do with the Regal. :TU:

Later

[BP_Motorworks]

Well,
I have a BBC Chevy that I am supercharging by a centrifical. (Very far from being done) There are a few reasons why I like the centifical over the turbo.
1) Less plumbing
2) It is about the same price and can be less depending on
application
3) If you are drag racing, you have to spool up a turbo at the
line. This causes inconsistent 60 foot times and plus, you
are usually on the trans brake when you are doing this
which causes excessive heat to your trans. (NOT GOOD) A
centrifical does not require the spool up like a turbo.

The only draw back I see is that a turbo is about 90% efficient,
while a centrifical is only about 70 to 75% efficient. (The best roots are only 65% efficient)
Keep in mind a big bore short stroke is recommended unless you have a heavy car. (3200 plus) Mine has a 4.350 bore but is only 439 cubic inches. Just a thought.

Blair

:stmad: :stmad: :stmad:

[69RivieraGS]

Reviving this thread from a while back:

I've been giving the Twin Turbo BBB idea some more thought. I'm currently working on converting a BBB to EFI using a SPX manifold and a Megasquirt EFI system. EFI definitely makes forced induction a lot easier.

Now, given the inherent structrual defeciencies of the BBB it seems like some can be helped with twin turbo.
IE: you can get big power and not have to spin as fast nor run a huge cam. A more moderate cam can alleviate lifter bore problems since springs don't need to be super tight(ie: no lifter bore girdle), and you also won't need expensive roller rockers.
Not spinning it as fast means you won't need a block-girdle as quickly. Granted it'll be pretty easier to hit the ~600hp barrier with twin turbos even on pump gas with decent heads and a moderate cam so eventually you'll need a block girdle anyway.

Of course there'll be power left at the table using this method, but it helps in not having to build such a crazy motor to jump start you to the 600hp mark especially if you have some DIY fab skills and turbo connections...

And if you get the boost up there you might start needing girdle+halo, or a new aftermarket block.

Just some thoughts... :idea2:

[69RivieraGS]

I'm definitely a fan of turbos...

I put one on my '94 v6 camaro and it took the ~3550lb car, 160hp stock 3.4L V6 from a ~16.5 @ 84.8 to ~14.2 @ 98.8 with running 10psi still on the totally stock motor(stock heads, cam, etc) but with tuning of course with enough fuel and the right spark timing. This motor also has 234,000 miles on it. It has a 9:1 compression and running 93 octane pump gas and careful tuning it has been living for years running this 10psi and being daily driven.

So taking the same precausions(tuning and oil modifications) with a BBB it should work well. But boost should be a bit more conservative, perhaps 5psi on the 10:1 motors of the late 60's, etc. But with nice heads and big turbos you won't need super high pressure to make good power...

[bobc455]

The only draw back I see is that a turbo is about 90% efficient,
while a centrifical is only about 70 to 75% efficient. (The best roots are only 65% efficient)
What do you mean by efficiency? It could be interpreted a bunch of different ways.

Thanks,

-BC

[69RivieraGS]

Yea. I would think one way to get an overall efficiency would be to:
1.)Get a baseline power for the N/A engine.
2.)Add power-adder, all else equal(nice in theory but not very good in practice...) but leave cold side disconnected from throttle body or carb and get another power measurement.
3.) Connect cold side and get another power measurement.

Eff = (P1-P2)/(P3-P1)

Although that's a bit unrealistic because to realize the real power potential for a FI engine you'd change a lot of things than from the N/A version.

[Turbo455]

I have a twin turbo buick 455 in my 74 camaro use a small cam and lots of exhaust. it works great. all the cheby guys ask why a buick:Dou: they think torque does not matter until they run me and then say how can i do that

[69RivieraGS]

I have a twin turbo buick 455 in my 74 camaro use a small cam and lots of exhaust. it works great. all the cheby guys ask why a buick:Dou: they think torque does not matter until they run me and then say how can i do that

Would you mind giving any specs on the turbos you're running? Cam specs? :laugh:

[Turbo455]

stock 1970 9.5:1 comp b4b intake demon 825 supercharger carb blowthru bonnet exhaust work on heads. 224/234 duration @.050 .480/.503 lift 112/108 lsa/lca there is another guy on here that runs an even smaller cam 212/212 i believe but i think if you could run a little moor exhaust duration it would be better like 212/224 no over lap mine has 5 degrees overlap and creates a little timing issues i run 4psi and thru a pair of t3/t4 .048 cheap ebay turbo's i think 400 for the pair new. the car weighs 4000lbs with 3.73 2400 stall runs in the high 11's on basically a stock motor. make sure you get head work done i tried to post pic put could not figure out how.

[Turbo455]

pics

[69RivieraGS]

Awesome. Thanks for posting the pics. What do you mean by .048? Trim? A/R ratio?
I have a single T04E-60/T3 turbo with a 0.8 A/R turbine on that V6(~204in^3) camaro I was talking about.

[Turbo455]

sorry it was a typeo i meant .48 but i looked at the turbo's and they are actually .50 a/r xspower brand turbo's

[Turbo455]

anyone out there interested in building a set of headers for my next turbo project i want to turbo charge my 72 skylark 12.80 455 or the 67 skylark

[69RivieraGS]

Who built the ones on your camaro?

[SS-TRUCK]

I realise you guys are talking about performance applications with the turbos , but I have a Chevy 454 dually for my tow truck and am thinking maybe turboing it . Any thoughts or advice ?
Thanks in advance .

[69RivieraGS]

One thing with a truck is you wouldn't need as big of a turbo(s). Since you're not likely to be screaming the motor through 6000rpm (at least I wouldn't think) you can go with one that responds better at lower/mid-range rpm levels that might run out of steam if you really wanted to open it up at high rpms. Smaller turbos usually spool up faster so you'll have the usable boost sooner. They'll also give some good torque in higher gears/low rpm with WOT since they spool faster and that's probably what you'd want for towing.

[ghostrider]

I too am in the midst of creating a twin turbo 455 setup for my 70 Wildcat. I've seen it done with other large car makes, launching off idle 2.78 gears, low 10's in a 4500+ lb car.

Its just that major WOW factor. It was my incentive to start.

[Turbo455]

a local exauhst shop fabed the headers for my camaro but it was a lot of $$$2500$$$ and i just am not willing to spend that kind of money again i think i have another shop here in oregon that will build them for $800. i guess i could do it myself but i dont know how to weld. :(

[SS-TRUCK]

One thing with a truck is you wouldn't need as big of a turbo(s). Since you're not likely to be screaming the motor through 6000rpm (at least I wouldn't think) you can go with one that responds better at lower/mid-range rpm levels that might run out of steam if you really wanted to open it up at high rpms. Smaller turbos usually spool up faster so you'll have the usable boost sooner. They'll also give some good torque in higher gears/low rpm with WOT since they spool faster and that's probably what you'd want for towing.

You are very right I will not be turning that motor 6000 . Just need some extra power since I am planning for a much bigger trailer . I need suggestions on where to find the needed parts , also some of the better brands .

[69RivieraGS]

I don't mean to discourage Turbo455 but I have heard nothing but bad things about XSPower turbochargers. There are tons of message boards around that warn not to buy them and warning to stay away from ebay sellers that sell them. I've heard anything from the cast compressor housings crack and break in half, to the reason they're so cheap is because the mix and match parts to make a turbo and don't bother checking tolerances or balancing the units.
Here's one particular post:
http://www.thirdgen.org/techboard/power-adder/325843-trying-warn-guy-about.html

One inexpensive brand that I have heard good things about are Master Power turbochargers. Master Power is a company in Brazill and I've seen several people use them for long periods of time with good results.

If you don't mind spending a little more money, then Turbonetics is a good place.

For wastegates, Tial is a good brand. Or you could get turbos with internal wastegates.

For general turbo stuff, www.atpturbo.com is a good place to get what you need.

I put together a simple Excel spreadsheet(attached: download it and change the .txt extension to .xls It wouldn't let me upload a .xls file) to try and size a turbocharger(s).
Simply enter your information for the variables(in italics) and then look at the end result of Pressure ratio, and Air Mass Rate(lb/min) and compare that to turbocharger compressor maps. There are many here:
http://64.225.76.178/catalog/compmaps/fig1.html

You can chose the RPM target in the Excel file where you'd want the most power or where you'd need it most. Then try and find a turbo compressor map that is near the center of those circles for the lb/min and pressure ratio. Those circles are called efficiency(shown as a &#37;) islands. The ones in the center are more effecient than the ones towards the outside. The lines with the tens and hundreds of thousands on them are turbo shaft speeds at those conditions.
For a twin turbo setup I divided the Mass Air Rate by two just to the right of the total for the engine.
These calculations are a little simplified since the temp doesn't directly corrilate to the pressure of the air...since air heats up when you compress it. But it doesn't have a huge affect on the numbers.

To me, for moderate levels of boost and a peak around 4200-4500, a TO4E-60 compressor looks pretty good. It would start to run out of steam, or at least efficiency around 5500+. That is for a twin turbo(2 TO4E-60s).
There's also the turbine to think about. The turbine really has a lot to do with how the turbocharger spools and how fast. A lot has to do with A/R ratio of the turbine housing. I would think with a twin, if you again wanted boost early and don't care about upper rpms an A/R ratio of about 0.6 on the turbine side for each turbo should do pretty well. It will start to choke the engine off some though at higher rpms.

I'm thinking of doing a twin turbo on my BBB but for performance. I'm thinking about going with two T70 turbos.

[69RivieraGS]

Ok, I changed it around a little. I added some fuel stuff and also made the temp corrispond to the boost pressure run. I also added a volumetric efficiency of the engine of 85%.

This is still of course a simplification. There are tons of different ways you could set up your engine to make things different here. This is just textbook stuff, not real world, but it's still a good place to start.

Just keep in mind that the fuel requirements are directly tied to the RPM entered. So if you go higher, you'll need larger injectors.

Again, download and change the .txt extension to .xls

[Turbo455]

I saw the same posts about sxpower as well but it was after i already installed mine. no problems so far. and as far as the a/r my twins are .50 and i could get 6000 rpm's no problem i only know that because my check valve for the trany went bad and the boost was not allowing the th400 to shift. I fixed the check valve and it started shifting at 5000 again. But I have a boost creep problem do you think that it is because i should run a .6 a/r instead of a .5 a/r. and yes i am sure the waste gates are working however the waste gates maybee to small.

[Turbo455]

Again, download and change the .txt extension to .xls[/quote]


Cool calculator. Nice Job:TU:

[69RivieraGS]

Also, here's a good resource for turbo stuff:
http://www.forcedinductions.com/

Also check out the Turbo Selection 101 and Turbo Engineering Explained.

[alan]

I saw the same posts about sxpower as well but it was after i already installed mine. no problems so far. and as far as the a/r my twins are .50 and i could get 6000 rpm's no problem i only know that because my check valve for the trany went bad and the boost was not allowing the th400 to shift. I fixed the check valve and it started shifting at 5000 again. But I have a boost creep problem do you think that it is because i should run a .6 a/r instead of a .5 a/r. and yes i am sure the waste gates are working however the waste gates maybee to small.

I've wondered about keeping the a/r smaller and using larger wastegates to bleed off the excess exhaust flow. I don't know if this would allow you to "have your cake and eat it, too" or not. (faster spool up without the restriction in the upper rpm range)

[sean Buick 76]

One thing with a truck is you wouldn't need as big of a turbo(s). Since you're not likely to be screaming the motor through 6000rpm (at least I wouldn't think) you can go with one that responds better at lower/mid-range rpm levels that might run out of steam if you really wanted to open it up at high rpms. Smaller turbos usually spool up faster so you'll have the usable boost sooner. They'll also give some good torque in higher gears/low rpm with WOT since they spool faster and that's probably what you'd want for towing.

I'm using twin T-3/T-4 hybrid turbos since they will spool up quick and still have huge capacity!

[69RivieraGS]

I've wondered about keeping the a/r smaller and using larger wastegates to bleed off the excess exhaust flow. I don't know if this would allow you to "have your cake and eat it, too" or not. (faster spool up without the restriction in the upper rpm range)

Hmm...I don't see why the heck not. One thing to make it more controllable however would be an electronic boost controller. Since a large wastegate on a small turbine could make for some really jumpy controls. If you had a nice controller it would just barely start to crack the wastegate open when you want boost and then fully open it at higher rpms. Even then, a large valve coming off the seat might cause a large loss in turbine inlet pressure, meaning losing boost. I think it would be tricky to make it respond well. Now maybe a multi-stage wastegate would work. Say one small one that'll control the small turbine well, and then at higher rpms open up either an additional small one or an additional large one. It's still something to wonder about however that pressurized air is like anything else in that it will follow the path of least resistance. IE: a large open wastegate might be easier to flow through than the restriction through a turbine and the turbine will lose speed, losing boost. But it might be made to work...

[69RivieraGS]

I saw the same posts about sxpower as well but it was after i already installed mine. no problems so far. and as far as the a/r my twins are .50 and i could get 6000 rpm's no problem i only know that because my check valve for the trany went bad and the boost was not allowing the th400 to shift. I fixed the check valve and it started shifting at 5000 again. But I have a boost creep problem do you think that it is because i should run a .6 a/r instead of a .5 a/r. and yes i am sure the waste gates are working however the waste gates maybee to small.


By boost creep do you mean it slowly increases past your desired max boost? Does it do this gradually and continually with increasing RPMs? I would say it's from a small a/r and wastegate like you said.

You may be able to get to 6000 no problem, but does it feel like power is leveling off or decreasing? Although that might be hard to tell if the cam and heads don't like breathing much up there. I've heard the old stock ignitions don't really provide much up there either.

[BadRiv73]

I'm going to run 2 Holset HX55 or H2D's, there off diesel trucks, there cheap, and made very well. Just thought I would add.

[Turbo455]

By boost creep do you mean it slowly increases past your desired max boost? Does it do this gradually and continually with increasing RPMs? I would say it's from a small a/r and wastegate like you said.

You may be able to get to 6000 no problem, but does it feel like power is leveling off or decreasing? Although that might be hard to tell if the cam and heads don't like breathing much up there. I've heard the old stock ignitions don't really provide much up there either.

it gets to desired max boost(4psi) almost instantly about 1/2 way to 60 foot then the boost slowly creeps up by 1/8 mile it gets to 8psi by 1/4 it gets to 12psi.

as far as 6000 it does not feel like power is running out at all. before turbos, motor reved slowly, with turbos it revs faster than any small block ive ever drove that includes a 2005 z06 6 speed corvette. if it is letting up i cant feel it. but i normally shift at 5000-5200 on street legal night and on bracket class 8.20(1/8) i sift at 3200 and pull the timing down to 2deg and still run 8.15 if the air is right otherwise it will run 8.25. by the way i beat the z06 by about 3 cars on street leagal nights(heads up) he hates my car.

[Turbo455]

I'm going to run 2 Holset HX55 or H2D's, there off diesel trucks, there cheap, and made very well. Just thought I would add.


there is i guy running one of those big disel turbo's on his trans am 455. do you think that 2 might be to much. just curious
http://www.highperformancepontiac.com/tech/0309pon_1979_turbo_trans_am/index.html

[69RivieraGS]

Wow...4 psi setpoint to 12psi...that's some creep!
Usually you think about it on the order of 1-2 psi. You pull the timing down to 2* BTDC? Wow. I have to pull the timing back to ~12-13 on a hot day on my 94 V6 with the 10psi I'm running and 9:1 compression. But I could understand that with 12psi on a 9.5:1 motor. Wow....
Do you have any idea of your air/fuel ratio at those levels? Must be pretty rich if it's surviving. :3gears:

If you can't control the boost any more than that I would definitely think it's the size of the wastegates and/or turbine housing size. That V6 of mine has a 0.8 A/R turbine housing that is actually a T3 housing but the turbine wheel is a P-trim T4, and it's a 204in^3. So double that and it's only 408in^3...still a good bit lower than a 455in^3 if you put two of them on it. The V6 doesn't spool super quick, but it does pretty good. I bet your exhaust backpressures are pretty dang high.
What size wastegates are you running? Are they internal or external? I would think 38mm externals would be a good size.

[Turbo455]

i'm not sure on the size i think 35mm external each side ill have to check and get back to you. but thats not all, the shop that built the turbo headers used 1 3/8 primary tubes. He said that was to keep the turbo lag down. but in my opinion the tubes should have been 1 7/8" - 2" regardless of turbo lag. I think that this is also a source of my boost creep. Ill tell you what, if i had to do it over i would have done things a lot different. I do value your input a lot. it has helped to confirm a lot of what i thought.

[alan]

1 3/8" sounds too small. Mine are 1 3/4" and the boost came up very quick with .69 a/r housings. After I changed to a tighter converter it wouldn't control the boost until I changed to Turbonetics race gates.

Take the wastegates off and see if you can still build boost! I know it sounds silly but I've heard of the exhaust velocity being so high that it would do that. If it makes boost with the wastegates removed, you'll need to do something other than just changing to larger wastegates.

[Turbo455]

1 3/8" sounds too small. Mine are 1 3/4" and the boost came up very quick with .69 a/r housings. After I changed to a tighter converter it wouldn't control the boost until I changed to Turbonetics race gates.

Take the wastegates off and see if you can still build boost! I know it sounds silly but I've heard of the exhaust velocity being so high that it would do that. If it makes boost with the wastegates removed, you'll need to do something other than just changing to larger wastegates.


i took the springs out of the wast gates and yes it still built boost it took all the way to the end of the track but it still reached 9 psi. that is why I said it should be 1 7/8"-2". I know it is not because turbos are to big because i also took one turbo out of the loop and the car actually lost power in 3rd gear and started slowing down. did you make your own headers.

[69RivieraGS]

The racegate is a 1.625"/42mm wastegate? That should help quite a bit. By tighter converter do you mean one with a higher stall? So the RPM comes up faster? I'm a bit new to turbos and autos...

I know a guy with a 427 LSX that he just built up for a 4th gen trans am. He's running two T70s with a 0.68 A/R turbine housing and two 38mm wastegates. He ran the same setup on his 350 LS1. He says he's starting to run out of turbo at 1090 wheel hp and 19psi, 109 race gas.
So that's a comparison point on displacement anyway.

[69RivieraGS]

i took the springs out of the wast gates and yes it still built boost it took all the way to the end of the track but it still reached 9 psi. that is why I said it should be 1 7/8"-2". I know it is not because turbos are to big because i also took one turbo out of the loop and the car actually lost power in 3rd gear and started slowing down. did you make your own headers.

Was the boost with the one turbo still above the set point? I'm assuming the springs in the wastegates are 4psi springs?
I believe you'd lose power, getting half the flow. But did it still overboost? I still think a T3 turbine may be a bit small especially with a 0.5 a/r housing. A T3 turbine with a 0.5 a/r housing still flows less than a T4 turbine with a 0.5 a/r ratio. So just comparing a/r ratios across different turbines isn't a fair comparison.

[alan]

did you make your own headers.

Yep. I couldn't find anyone at the time who could tell me what size tubing to use so I guessimated 1 3/4" should work. It's not a bad size and I almost wonder if 2" would be too much unless the primaries were really short.


By tighter converter do you mean one with a higher stall? So the RPM comes up faster? I'm a bit new to turbos and autos...


Lower stall. It loaded the engine more at a lower RPM.

[69RivieraGS]

Ah, ok.

Yea, I think if you get too big with the primaries then you really start to lose exhaust gas velocity/pressure.

[Turbo455]

I had said earlier that it had 1 3/8 primary tubes i measured them today and they are actually 1 1/2 OD i still think that is to small what do you think.

[alan]

I had said earlier that it had 1 3/8 primary tubes i measured them today and they are actually 1 1/2 OD i still think that is to small what do you think.

I just measured an exhaust gasket port, and the area is 2.184 inches. The area of a 1 1/2" dia tube is 1.485 (that's assuming it's 1 1/2" on the outside with a .0625 wall).

1 5/8" tube area is 1.767"

1 3/4" tube area is 2.074"

1 7/8" tube area is 2.405"

As far as the tube size goes, I may need to back up a couple of steps. Here's a quote from another board concerning header tube size and HP numbers:


My headers are only 1 5/8 which matches the exhaust ports on the heads. I have seen small blocks make 1600+hp on 1 5/8 primaries. 1 3/4 will make 1800hp and more. 1 7/8 for 2000hp and over. We are using 1 3/4 on an 18 degree headed small block in a buddies ride which will make 1700+. We usually just match the exhaust primary to the port or maybe a little larger just to keep things flowing smoothly.


Depending on how fast you want to go, you may be better off to spend your money in other areas before upgrading to a larger tube size.

[69RivieraGS]

Do you think it matters what kind of things you have after the headers? It sounds like from that quote that they're talking about naturally aspirated engines. Possibly race setups without mufflers? If you had some larger exhaust restrictions down-stream of the headers would you want some larger primaries to act as a kind of buffer? Or am I just making things up? :Dou:

I'm not sure how this would come into play with a turbo setup though. I just know that you want to balance between turbine inlet pressure and reversion. If you have a high pressure drop accross the turbine velocities should be high and you should get a good spool rate. This means high pressure between the engine and turbocharger, and lower pressure(free flowing tailpipe and mufflers) after the turbo. But the bad thing about high turbine inlet pressure is it means high backpressure on the exhaust valve and if you have a cam with overlap you'll get reversion, or at least not as good exhaust purge and the intake charge will become a little inert making combustion not as good.

[alan]

It sounds like from that quote that they're talking about naturally aspirated engines.

Nope, that's with turbos. I was suprised that so much power could be made with small primary tubes, but that's good news!

[Darryl Roederer]

I realise you guys are talking about performance applications with the turbos , but I have a Chevy 454 dually for my tow truck and am thinking maybe turboing it . Any thoughts or advice ?
Thanks in advance .
This might sound really crazy, but if it were me, I'd buy a rusty 10-15 year old school bus with a 5.9 cummins diesel and an Allison 545 auto trans for $1800 and swap that drivetrain into your tow rig.

The allison/cummins combo is 100% bullitproof, will last 1/2 a million miles, and give better MPG than your stock 454. Also, you can EASILY crank a diesel up to un-real HP levels for just a few bucks.

After the swap, Ebay off the 454, a few of the school bus pieces, and send the carcus to the scrap-pile, and you could actually turn a profit on the venture!

As a bonus, you could then run the diesel on free fuel!!!
See here:
www.frybrid.com

[69RivieraGS]

Ok...yet another revision of the turbo/engine calculator.

This one includes a table based on rpm that has things like: turbo air requirements, fuel injector size, and if you enter the fuel rail pressure higher than standard you can see what injector size you can buy and run at that pressure to get enough fuel.

Again, save/download as .xls instead of .txt.

[69RivieraGS]

Well I'm one step closer to TT Buickness. I picked up a couple of used turbos and wastegates from a guy who needs to upgrade for his 427 LSx to bigger ones.

Alan, would you mind letting us know your compression ratio on that 455? How much boost and ignition timing?

I'm thinking about trying these on my stock rebuild 430 with a SPX manifold converted to EFI. Since the stock compression ratio of this '69 430 is 10.25 I'm going to have to be pretty moderate on the boost with 93 octane.

I pretty much just need to start fabricating(starting with the intake). Anyone want to estimate what kind of power I'd make?

As for the throttle body, I'm thinking about building something simular to this:
http://www.intakeelbows.com/universal.htm

The turbos are two MasterPower T-70's with a P-trim T4 turbine and 0.68 A/R ratio. Wastegates are two 38mm Tials.

http://www.turbocamaroproject.com/TT430/TT430.html

[Turbo455]

I pretty much just need to start fabricating(starting with the intake). Anyone want to estimate what kind of power I'd make?




Check out http://www.turbofast.com.au/TFmatch.html
it shows that with 10.25 comp you will only be able to run 3-4 psi with a 75 VE and you should make 500HP

That is unless you are going to Intercool or alcohol inject then of course you would be able to run moor boost

[69RivieraGS]

I agree I should heed caution, but it looks like that calculator has a pretty big safety factor built into it. I entered my specs on that turbocharged V6 camaro I have with 9:1 compression and running 10psi boost and 85% VE and it tells me I need to be running 102.8 octane. I've only run 93 in it and while I have to tune the ignition down to near 13 BTDC it does run well and has been for several years.

Even your combination: 4.313/3.9 (assuming stock bore), 9.5:1, 85VE, and you've said as much as 12psi boost when it creeps: 107.8 octane.

While I do agree high static compression and turbos don't mix, I think it's worth a cautious try.
Does anyone happen to have a good feel for stock 430 volumetric efficiencies with stock heads/cam?

Eventually if I want to see some real numbers I'll have to have a nice built 455(with girdle) and at that time I could have some lower compression built in. It would also match the Stg 2 SEs a little better as well.

[alan]

Alan, would you mind letting us know your compression ratio on that 455? How much boost and ignition timing?


8 to 1 compression and 32° timing, with 1.5° pulled out for every pound of boost. 8 lbs of boost would knock the timing back to 20°.

[69RivieraGS]

8 to 1 compression and 32° timing, with 1.5° pulled out for every pound of boost. 8 lbs of boost would knock the timing back to 20°.

Wow, ok. That's some nice timing for a turbo motor. I wonder if a cam with a late closing intake valve could be used on a higher comp. motor to bleed off some compression. Although most cams with late intake closing are made for high compression motors and have huge duration (lope) and lots of overlap. And overlap is definitely not wanted on a turbo motor, at least a street turbo motor where the exhaust manifold pressure at the valve will be higher than the intake manifold pressure at the valve. And then if one would spend money on a cutsom grind cam they might as well build the motor that would be best for it too...

[Buicks4Speed]

Put in a bigger cam and that will help. If you need to drop the compression, just buy a thick set of Cometic gaskets. OR buy a set when you blow out the stock ones. Run a Boost Cooler setup. Will be money well spent for a street car. You can get a controller that runs "washer fluid" progressively off the amount of boost.

[Nitro71455]

Put in a bigger cam and that will help. If you need to drop the compression, just buy a thick set of Cometic gaskets. OR buy a set when you blow out the stock ones. Run a Boost Cooler setup. Will be money well spent for a street car. You can get a controller that runs "washer fluid" progressively off the amount of boost.


I think Rick hit it on the head......

[69RivieraGS]

Hey Nitro71455, would you mind sharing your static compression ratio with that 12psi on pump gas? Are you also running a pretty big cam? You have more flexibility with a supercharger vs turbo since you don't have to worry about the exhaust backpressure issue.

[69RivieraGS]

If you need to drop the compression, just buy a thick set of Cometic gaskets.

Are these any that TA carries? I saw their multi-layer ones that go up to 0.054". Then there are ones that require o-ringing the block that go up to 0.125". Based on a 430, and a stock gasket thickness of 0.020", moving up to a 0.054" gasket would drop compression from 10.25 to ~10.18. And a 0.125" gasket to ~10.05. That doesn't seem like a worth-while drop to replace headgaskets. Unless like you say, the stock ones are going to squish out without much effort. I won't get to crazy on this setup. To get serious, eventually I'll have to build up a speciatly 455 with extra head bolts using the Stg 2 SEs.

[Nitro71455]

Hey Nitro71455, would you mind sharing your static compression ratio with that 12psi on pump gas? Are you also running a pretty big cam? You have more flexibility with a supercharger vs turbo since you don't have to worry about the exhaust backpressure issue.


I'm currently sitting at 9 to 1 compression wise thinks to the .130 thick Commetics Head Gaskets.

I also found a good progressive Alky kit was worth it's weight in gold.

I'm still running a small cam (crower) that's not real boost friendly.

Intake is .518 on a 230 duration
Ex .519 on 236 duration
Lobe seperation is 112

I run my timing at 30 to 31 degrees total and have for the last 3 years.

--Rich