air fuel ratio with boost
 

Just saw stock fuel map for a ZR1 vette engine. 9:1 static and 10psi boost. Anyone wanna take a guess at what the stock wot Afr is under boost ? :)

What year ZR1? I am going to assume around 12.2:1 or leaner.

2009+ years.

nope

what fuel ?

Stock ZR1. Premium pump gas.

i,m sure they don,t run it on the ragged edge .i wont guess because i know the answer but don,t want to cheat.

Ok I don't wanna jerk anyone around.

10.7 at 4000rpm

Above 5000rpm 10.4.

funny thing,when i mentioned running 10.5 on a 1200+ hp engine some members said i had no idea how to tune an engine.i guess gm engineers don,t have a clue either,lol.

Sounds about right to me!!

Also seeing some talk about the stock ford mapping for the supercharged cobra in the low 10 range AFR .

As far as the Vette engine , obviously they are shooting for safety. And supposedly the stock blower causes some high IAT readings.

I'm sure there's some power on the table by pulling a bit of fuel out, but I don't see a ZR1 blowing gobs of black smoke and washing the rings out of it .

Now remember that is in a rolling vehicle, the load on a marine motor would justify this even more. IMO

And its a modern EFI engine with knock sensors, iat temp sensors, port injection, etc. A far cry from a carbed marine engine with poor fuel distribution, no iat sensors, no knock sensors, etc.

Late to the game, but my guess was going to be in the 10's... Our 07 Whippled Shelby (5.4) is set up between 10.2 and 10.8. I run the boat in the 10's also.

i think people would be suprised at how little the power loss is going from 11.8 to 10.5.i don,t know the afr on a merc 1075 but il bet it,s not 12.1.

Oh come on had to be "beginners luck" LMAO!!

Don't bet
The 2 I've put widebands on would run in the 13 at cruise and only drop to 12.7/9.real scary,tried adjusting regulator for more fuel up top and it did nothing but richen the bottom a little.ended up having Marc boos add some fuel.
And the timing they run,wow.I'd never tune like that.

So the 1075 merc is 12.7 Wot?

Heck my gas GM dually is 12.6 at wot.

12.6 hp ?
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Lol.

Remember these are 7.9-1 compression,,but yes they were lean and they had like 36degrees of timing to 2lbs of boost.then backed down to 32 degree.
But 13lbs of boost was 12.7ish to 13.3 depending on load.the motor has a fuel pressure compensation table and we brought it up to it's limit.tried to cheat it a little.
Boats were 42 and 46 outerlimits.

I wish I could find the article posted here written by a GM engineer that worked on the northstar.

Summary, detonation must be avoided in all instances to prevent premature engine wear. It's impossible for fuel systems to react quickly enough to instantaneous changes in load conditions or fuel distribution issues. Therefor under wot and wot transitions stock calibrations will be in this range.

No disrespect to all the garage engine building gurus but there's a reason they are the engine calibration experts at the #1 powertrain company in the world and you are a plumber. They've got millions of dollars and instrumentation you could only dream of.

Do you really want to go on the expert opinion of an internet guru and risk your engines at 13 to 1 when engine failures could cause you major economical hardship? No thanks

I agree hogey .

While I know there are a million variables, I think somewhere along the lines guys assume that anything richer than 11.5 you are blowing raw fuel out the pipes, washing cylinder walls, and diluting oil.

On some of these setups a simple change of 2 or 4 jet sizes will put you from "ideal" to "overly rich" on paper. How many guys have been a couple jet sizes to high over the years from their fastest mph? Did going 2 jet sizes higher blow gas out your tailpipe ? Did the boat lose 10mph?

Well my lm2 has tuned many of high hp boat engines and race cars.what I saw,,is what I saw.and if you don't believe me,give Marc at prescion a call and he'll verify what I saw.
I gave you the info,,do with it what you want.

I remember seeing a dyno sheet from a 1075 mark did. I was shocked to see the air fuel around 12.0. But if it works it works !

And that's after he adjusted it.

This is a very open-ended argument some motors are built to withstand more heat some aren't. I think the right afr's is a very application specific number. Some forms of endurance racing run as high as 20. Yes 20. The motor has to be built and tuned for it. 12 may work for one motor and not another.

You're comparing the reliability of a 1075 with a 50hr service interval to an LS9? Not even in the same ballpark. A 1075 will never accumulate enough hours on a set of pistons to see the effects of wear due to small and persistent amounts of knock. Whereas the LS9 could potentially see up to 200k miles, granted not at the same loads.

Well when your watching the sensor and in particular the knock sensors and you see them quiet.it's a good thing,even as lean as I've seen it.and a few others who were sitting in the back seat with me.
These to motors are both over a 150 hrs of run time,with a lot of it in the 5000-6200 rpm range.it's the running joke that they've run the equivalent of the eastern sea coast at 5000+ rpms,in one season.

The new direct injected motors are set up to be very resistant to detention.

:rolleyes::rolleyes::rolleyes:
Well there you have it. Everyone should target 12.7 then because anecdotal evidence :rolleyes:

Can you read,,,I said this is what we saw.we tried a quick fix,it really didn't work.we sent the computes out to be reprogrammed.12.7 is a grenade waiting to happen.alot of 1075 owners don't have a clue what's happening in their combustion chambers,,hope they'll look and get a retune.

Im very surprised its that rich, the cats must be pretty upset when its that rich.

Guess what EGT's the Ford ECOboost can resist for hours on end????

I've read everything you wrote and you never made that clear.

:rolleyes:Seem pretty clear

Mercury runs the 1075 on the lean side. At WOT they get closer to 11.7/12.0afr ... cruise range is in the high 12s, low 13s .. Mercury, Whipple , Mark Boos are the only ones i know that have the software to make changes. the only thing you can do is crank up the fuel pressure from 60 to 62lbs to try and cheat the computer.. anything more the computer knows bc it monitors fuel pressure. Also the 1075 will go 150-175 hrs no problem, then just change springs,lifters, rockers and belts etc

Some good info in this thread, and I thank you guys for it.

Probably about the same as a 1075.... They have about the same refresh schedule, don't they? :poopoo:


(Sorry, had to take the slow pitch down the middle. )

What are the readings from 650-4000 RPM though?

Here is my thought. The Corvette is direct injected so they can control spark knock WAY better, but the intercooler has a finite supply of cool water, so to compensate, just flood the engine.
The 1075 on the other hand has an unlimited supply of cool water for the intercooler, so they can run it leaner and with more timing.
And another thing is how good would it look for GM to say you have to have the engine in your $120,000 car rebuilt every 6-12 months, vs Mercruiser, say Oh you just bought 2 of our $80,000 engines, the maintenance schedule on those engines is a rebuild every 150 hours, but that is OK because we know you can afford it, and that is the accepted norm for your type of boating.

Listen guys. The ZR1 is NOT direct injected. ZR1 is a C6. Direct injection made its debut on the C7.