Ok before I say anything, I am wondering how are some imp cars running 1.5+ bar of boost, even 2.2bar with PUMP GAS, how do I know? A friend of mine has an inline-6 5liter single turbo 4wheeler that does 850insh rwhp at 2bar of boost.

I know well get into the discussion of dynamic compression ratio and formulas, but even those fomulas can't explain whats happening, i hope someone can chime and provide some insight.

8.5:1 CR + 2.0bar of boost and 93octane pump gas.

Why are low-comp Vettes not able to run more than 12ish PSI (which is less than one bar) without at least methanol or race fuel.

I understand that the possibility might be that people dont want to take the risk of damaging their engines and that makes sense, but other than that, any ideas?

How much boost would you go with a 9.5:1 CR and 93 pump gas?

 

Very, VERY open ended question, waaaaaaaaaaaay to many setup variables to give an honest answer...
only answer I can provide is, as much boost as that setup can handle for optimum AFR...

 

Say that you have prevented the LS7 engine from lifting the heads with 5/6 bolt heads and block, head studs, o-ringing ect. at high boost pressure. You still have a tremendous volume of highly heated air to cool down to acceptable IAT's that a 427ci engine would require at 2 bar of boost. The intercooler(s) would need to be massive and super-efficient and I don't know if the Corvette frontal area allows for the transfer of that much heat load.

My guess is the heat load requirements are too great for a large displacement motor, pump gas, limited frontal area and high boost. I would also guess that more efficient intercooler design is a big part of the solution.

 

Thats a good answer

The other cars I mentioned are running HUUUUUUUGE intercoolers for starters...

 

the other cars are also tiny engines in comparison... very VERY easy to make "Big" boost with a smaller air pump (engine) I had a '97 supra 3.0 with a 91mm turbo that made 30+ psi soooooooooooo easy, and 17psi on pump all day long, but the real issue is IAT's for your climate, a methanol injection system is the way to go... promise...

 

There is one very simple answer to your question:

Because Corvette Engines Were Never Designed, Developed, or Intended to be run under boost!

That simple answer is rooted on more complex details: The LS series engines have two main things going against them when it comes to being run under high boost (again, because they were NOT designed to be run under boost):
1- High Compression. 10.9 or 10.7:1 compression does not lend itself to high boost levels, specially not without direct fuel injection. Look at a few boosted examples from the import world: Mitsubishi Evolution 8/9 4G63: 8.8:1 compression ratio, 20PSI (that's right. 20!) stock boost at 3500RPM, tapering down to 16PSI by redline. Subaru STI EJ257: 8.2 compression ratio, 14.5psi stock boost. You will seldom, if ever, see a factory boosted motor with a compression ratio of 9:1 or higher, much less in port injected engine, and even then those engines typically employ variable valve timing and often variable valve lift as well.
2- Inferior heads. Somewhere between two valves per cylinder, no adjustable valve timing, less optimized combustion chamber shape (clearly illustrated by the potential gains available from aftermarket head porting), and, once again, a head that was designed developed and inteded to be run N/A, the LS Series engines can not introduce enough swirl into the intake air mixture, nor adequately prevent detonation at high boost levels.

It gets more complex than that, but those are the basics. If you want to know what it would take for a Corvette engine to be run under boost, just look at the first and only LS engine that was designed to be run under boost: The ZR-1s LQ9 Engine has better heads and low compression, just like any other factory FI engine 9.1:1 compression to be exact, with what are arguably the best heads you can get for a GM smallblock today, and while warranty, emissions, and drivetrain concerns only have it running at 10.5PSI from the factory, rest assured it is able to hold off considerably more than that... Probably still not as much as a quad cam, dynamically variable intake and exhaust valve timing, 4-valve engine with a few decades of factory development for operation under boost, but then again, when you are displacing 6.2Litres, you can get away with low efficiency and still make exceptional power..

 

AIS on its way but its damn hard to find methanol here, even that fancy windshield washer fluid that we got it SOAP based, but ill start looking. I mean a gallon of pure meth costs like $280!!

And you thought we were ripping you guys off with fuel



Thanks, again a nice answer. im still wondering though, 640 BHP through 10PSI is quite low, can't seem to understand why

 

Well, it is 10PSI into a 9.1:1 compression engine though and under a 5 year, 100,000 mile warranty, through factory exhaust manifolds, factory catalytic converters, factory air intake, etc... Those same 10PSI into my LS2 are netting me closer to 700BHP with much worse heads and 0.2L less displacement: the extra compression helps a lot, and there is a HUGE difference between what can be achieved in an aftermarket setup where emissions, noise, and warranty are non issues, and what a major automaker is willing to warranty for 100,000 miles

 

You can buy the yellow bottles of "HEAT" from the auto parts start - they are pure methanol and about $1/bottle.

Also, you can order a 5 Gallon Methanol jug from VP racing for about $15 bucks.

To answer your question, I see 12.5 PSI with 17 degs of overall timing with a very efficient turbo cam and AIT's in the mi to low 100's on my 8.5:1 427. That's just under 870 at the wheels. I get away with 2 degs more of timing and 2 more lbs of boost on methanol.

 

I think you meant "HEET"


99% Methanol, 1% Soaps and surfactants, but it costs $2 per 12 Oz, so that's about $22/Gal...
Good find though; I always thought Heet was Isopropyl... Neat!

Unfortunately, it won't help our friend much... Something tells me that if there is an Autozone in Dubai, it won't carry this product
On the plus side, if he's OK with <700WHP or so, you can get that with straight up pump gas on any good kit that has a suitably large blower and a blower cam...

 

anti freeze? we got LOTS of anti-freeze hahaha...

Well as far as importing gallons of meth, I think there is a weird charge that we gotta pay over here to get that stuff in, seems ill have to ask, coz that price is dirt cheap, I might as well get myself some 50 gallons lol

 

Im thinking I can get away with 820ish on 93pump with 12PSi and 16degrees of timing, thats my calculation however, and 930insh with meth, 16PSI

 

Not sure where you are getting those calculations from, but that sure as hell won't happen on a stock block, and it probably won't happen with a built one either using the numbers you are quoting... Not on any accurate dyno at least
A&A made 778whp on pump, at 12PSI but that was with forged pistons, a stage 3 cam, worked heads, headers, and the largest blower Vortech makes that will physically fit in a Corvette. I'm running 14 degrees at 10PSI; I don't see how you will run 2 more degrees with 2 more pounds of boost in the desert heat, and even if you could, that won't produce 820ish whp, and if it did, you wouldn't gain 110whp just by adding meth without increasing boost...

A much more realistic goal for a pump gas Z06 is mid 600s on a stock shortblock, mid 700s with forged internals, cam and head work... That's if you don't like blowing your engine of course. And, btw, if meth is so expensive there, have you considered running race gas?

 

A lot of it comes down to how much an individual is willing to risk. While many combinations can make quite a bit of power on pump gas when pushed to the limit I like to tune with a margin of safety. The max I will allow my car to run on 93 octane is 13psi, 850rwhp, low timing, zero knock.

Engines are expensive and I personally don't feel the need to beat mine up with crazy #'s and cheap fuel. At higher power levels which I don't run on a regular basis I don't mind adding race fuel. Cheapest insurance out there.

 

In Oregon 91 is about the best you'll find, occasionally I've found 92.

 

Same for Nevada, Arizona, California and a lot of other states..
In Vermont I could buy 94 octane though... And a lot of stations in Illinois and Michigan sell 100 unleaded and 110 leaded...

 

110 unleaded? I've NEVER seen such a thing!!

I am jealous!

 

Don't be. I said leaded. I've never seen 110 unleaded either
The fuel is "Turbo Blue 110" and is sold at many Citgo stations in Michigan for off road use only. It used to cost $5/gal.

 

ahh, ok. Missed that part somehow. We have the same stuff at a station about 4 minutes from my house. Great on the ole 02 sensors, too! HA!

 

I'd run about 20 gals of it through my car before the O2s were shot