Dyno results 470 street engine

Duuude .. been quite a while and now I can see why :eek2::eek2:

Good Luck with the new Bullet

 

Its going back to the dyno this week, I changed a few things in the port work and have my fingers crossed we might see some gains but it could go the other way. This engine has been a challenge to say the least collectively waited 15 months for parts, machinist got a mosquito bite while racing in the US and was in the hospital for 2 months and almost died. Goals were to run on pump gas, pull enough vacuum to operate power brakes, 1.5 hour drive each way to the track and run real hard in a full weight small tire GS. I have another another build like this one that is going to be very similar and the goal on that one is 700hp.

 

Im just curious what kind of mpg does a car like this would it get on the 1.5 hour drive each way?

 

That all depends on much more than the peak HP/Torque #'s. From my experience driving BigRed for long distances through several motor / drivetrain setups

- Most importantly would be to keep cruise RPM slightly below where the cam is really starting to wake up and come on ..probably close to 2400-2600

- Having a torque converter that isn't slipping too much at that rpm

- having a final drive \ rear gear \ tire diameter combo that puts you at 65-75 mph at that rpm

I've seen well over 16 mpg @ 65 mph with a 500+hp setup. Spin it up to up to 75-80mph where the cam is waking up and it drops 4-5 mpg

.. and the flip side of the coin is now you're probably off at least .5 sec 1/4 mile time from where you'd be with a setup more optimized for e.t. than mpg

 

It would get about 25 mpg I'm guessing...

 

I see 25 or better out of similar combos.
Lower rpm does not offer better mileage potential for these engine paradigms.
If you are seeing a mileage drop from faster speeds it isn't the engine, it's power level at full throttle, rpm ,or assumed airflow through the induction system.
It's either lacking more timing/tuning at high vacuum or the car itself has hit the aerodynamic wall.
Get that sorted out and you will maintain mileage over longer trips due to less time being spent on the road.

 

Posted by 69GS400s

"- Most importantly would be to keep cruise RPM slightly below where the cam is really starting to wake up and come on ..probably close to 2400-2600

- Having a torque converter that isn't slipping too much at that rpm

- having a final drive \ rear gear \ tire diameter combo that puts you at 65-75 mph at that rpm

I've seen well over 16 mpg @ 65 mph with a 500+hp setup. Spin it up to up to 75-80mph where the cam is waking up and it drops 4-5 mpg"


This is about what I've got with the engine Chris built me.
2600 - 2700 RPM @ 65 - 70 mph. aprox. 18 -20 mpg. 180 - 190 deg.F water temp.
TH400, 3.08 gear, 27.5" tire, 3200 stall converter.
The converter does not feel like it's slipping at all, that I can tell. If I jump on it at that speed it pops up to 3200 -3400 and pulls like a freight train! So much fun!

 

Thanks Alan! I have not had a car for two Summers, but my time is coming.

 

Can't wait to see what happens with the next dyno pulls. I know you have put a lot of effort into this build and I thank you!

John

 

how can that be? more displacement, more rpms, same a/f ratio, more fuel used. HOw can lower rpms not mean less gas used if the trip time is the same?

 

Higher vacuum indicates less mass through the engine despite rpm for one, and less minutes on the road tilt the balance point of efficiency with raw consumption (less operating time over a long trip)
These things are covered in engineering education intended for OEM employment.
I've driven several as daily drivers for over 100k miles each. Possibly near a million miles of record keeping.

 

On engines such as these, there is a fairly narrow 'window' on where they'll see the best mileage--too low and more throttle (and less intake vacuum) would be needed for cruising, while on the other end of the spectrum, too high and it gets into the cam's powerband and starts to draw harder; both ends would be pulling more mass through the engine.

Either way, an engine with 450+ displacement is going to pull more mass through it than a 350+ displacement engine with similar intake vacuum (and similar mileage 'windows'), unless the power/weight ratio is so far off that the smaller engine would need more throttle to cruise, or the smaller engine used a more radical camshaft grind that produced less intake vacuum at any speed.

Less time on the road does equal less fuel consumed, but then "MPG" would stand for 'minutes per gallon' instead of 'miles per gallon' lol

When viewed in this way, it can make something appear much better. Much like running an engine cold while on the dyno to produce better numbers, or overclocking the CPU on a computer with a freon (AC) cooler will net higher benchmark numbers before the CPU has the potential to burn up.

I always get tickled when I see data size advertisements on hard drives which use decimal bytes instead of binary bytes (which the computer actually uses), in order to inflate the numbers and make it appear larger than it is. Ever notice that on your '500 GB' (as an example) hard drive, when set up on your computer, actually reads much less than 500 Gigs? Now you know!

 

What does a motor like this cost intake to pan roughly?

 

I politely disagree with that 'theory'.
It makes perfect sense though...
I'm not going to get into any specifics because they would be too particular to the application.
There's a lot of 'ifs' and an equal amount of solutions to those ifs.

I'll say that a complete understanding of the vehicle's attributes constitutes more of the finished result than the engine alone, for mileage.
The end result of that is absolutely the culmination of the vehicle tuner's efforts and abilities, a$ well a$ however long it take$ to accompli$h it when it come$ to paying for $hop time or working with said shop to coordinate efforts by virtue of buying compatible componentry...because the shop isn't making any money by giving away a stellar, world class combination.

 

Of course you're going to disagree, I wouldn't' expect anything less.

Well as long as it makes perfect sense, and would be true if certain ifs lined up with other ifs and one were willing to mortgage their third home for it, and you don't disagree with the rest of my post, I'd say I did pretty good at summing it up. :grin:

 

It isn't lucky circumstance that either Chris or anyone else get what they get out of their profession's work, under whatever metrics they use to measure the outcome.

It wouldn't be appropriate for me to outline how I get similar combos to see that kind of mileage on Chris' thread, or with too much information in Jim's forum. It isn't a matter of magically ending up with a lucky amount of coinciding 'ifs'.
The window is much wider than you think.
I am stating that the mileage should be good, in fact better than what hobbyists are used to expecting.

Nor is it appropriate for you or anyone to refute their work, or to suggest that maybe the flow bench or dyno #'s are off.
There are a few examples of engines similar to this delivering good economy, right here on this forum.

I'm saying this with great respect, because I value your opinion and input all over this forum, Gary...
In this particular circumstance your thoughts on this engine's capability on the street are somewhat misguided.
For example, supposing a smaller engine had a more aggressive camshaft and it were used to cruise with, you would definitely see good vacuum on the gauge if you were to cruise it at a higher rpm. I could cite examples of a similar sized engine using 270* @ .050" for cam and it still will create vacuum, albeit higher than most might think reasonable for a cruise speed.

Rather than offering negativity in the form of well thought out and convincing explanations of why you think something won't work or would only work under limited circumstances, could you use that awesome brain of yours to accomplish what what many have already shown to be possible?
I found my way by stumbling into a good combo that took years of education to explain.
This isn't a situation where anyone is appearing to make something look better that is not...
Any engine NOT made with similar attributes as a factory engine MUST change the paradigm of operation.

It's silly to throw stones at the aspect of costs, or saying a third mortgage would be needed.
I can't imagine anyone buying an engine like this, and paying the costs up front to save mileage down the road with that engine's sole purpose being mileage alone. Engines like this and similar others are a gift to the hobbyists world because you can have your cake AND eat it too.
These hot rods and toys are engineered to deliver what the owners want out of them, in this case roughly 650hp.
They aren't particularly 'cheap' in the first place.
It would be a greater irresponsibility if I were to disclose what my costs were on the aftermarket cylinder heads I've brought to market based on how many units were guaranteed by the foundries under contract or by projected sales.
Suppliers and engine builders have to make $$ in order to deliver you their craft.

I have nothing to gain here for myself directly, nor am I in collaboration with Chris.
Notice that I am here promoting someone else's impressive craft, rather than bashing anything about it.
I don't appreciate the negativity in this post, especially when it's coming from someone who probably hasn't built a similar engine and run it on the street. If you have run one and haven't seen the claimed mileage, keep plugging away...you'll get there.

 

I, for one, am very curious as to how to wring out 25mpg from a 500-600hp motor. Just behind you, I've probably put well over 500,000 miles on my Buicks over the past 30 yrs .. most in that hp range.

If you are familiar with Larry "The Wizard's" 600hp motor built by Jim .. and his Stage1 with GV overdrive, he has maxxed out @ i believe 16+mpg.

I'm no pro .. but I can turn a wrench and tune a V8 pretty well. The best I've ever seen consistently is 18-19 mpg on a stock GS400 W/ 2.93 rear gears and very close to that in a stock SportWagon 400 W/ 3.23 gears. Also of note was a low mileage 69 Sky 350/350 2barrel that despite every effort coudn't best 15mpg

 

I guess either keep turning wrenches to get the same results you've always seen or study more engineering of induction systems.
A good primer is the books on emissions and the combustion event itself, as they will force you to create formulas to quantify your changes made before you create your engine, cast and machine it, and then test it's design.
[Since we aren't creating one from a fresh sheet of paper, apply your education to an existing platform, such as the already well designed Buick]
I've logged closer to a million miles with those power levels and that mileage.
I'm saying that it's entirely possible. It's up to you to get yourself there.
The power level of the engine at full throttle has little to do with how it operates at part throttle.

I suppose one can play with tuning and driving styles endlessly until they figure out each combo, or plan out their theory, quantify and prove it on paper and then execute it.

 

I believe I've stated that my experience is with very similar engines to this and isn't theory.
The tech speak using theory is only necessary when people are attempting to convey quantified information between each other.
I'll definitely agree that Johnny Angel won't be too concerned about it either.