HerBlueDevil

so took the car to a local shop, getting cold air intake installed and pulley kit from lingenfelter and a custom tune. the first Dyno is stock.

Kingspoke

Thanks for posting. I'm always amazed at the percentage of HP (reported as 650) lost through the drive train, in this case 17%, seems high on these cars. I'm gonna guess you have an automatic, but it still seems high to me especially with the efficiency of new technology transmissions. Can anyone explain this? Thanks.

tail_lights

I can't, but I wonder right along with you. I also find it strange how the autos seem to dyno lower but (as reported on here) consistently trap (by a pretty good amount too) higher than their manual counterparts.

OP thanks for sharing! Looking forward to the results!

3 Z06ZR1

I agree nice numbers!

The reason the manual dyno's more but are slower in SOME measures than the A8 is the gearing.

The A8 has a 10.99 overall low gear vs the 7.86 overall low when in first of the M7 manual.

Some the A8 gets 11 spins of engine to 1 spin of the rear
vs the M7 geats less than 8.

Then the A8 enjoys the momentum through the 1/4 mile from the quicker 60 ft from the gearing advantage thus the higher traps from a STANDING start.

Where the M7 shines when the roll race comes in and start equally with more equal gearing the A8 then enjoys no momentum advantage from the lack of a standing start.
The experienced manual driver can put the car at such speed where
the manual is in the sweet spot to go and can then use its horse power advantage.

The manual depends fully on the drivers skill!



Can't beat engine direct to gear.

HerBlueDevil

yes it is A8 and we are 1 mile above sea level. some people say it shouldn't matter since its supercharged but some people they say it does. I do know one thing for fact, every year when they have the top fuel and funny car races here in Denver, they do replace there supercharger pulleys with a smaller ones to compensate for the thiner air.

HerBlueDevil

so here is the Dyno results, not bad so far. more mods to come.

FastMatt2

only people that say that are people that live at sea level , The dynos you posted are SAE corrected for altitude, if you have them give you the uncorrected numbers you would be down by about 20%. Uncorrected your car would have been putting down about 460ish rwhp stock.

dar02081961

Both schools of thought are correct some of the time.

Seriously it depends on how much excess boost the supercharger normally produces. In other words at sea level how much boost is released by the wastegate normally? That extra boost that is being wastedgated at sea level is all of the head room you get with the supercharger when you climb in altitude. The supercharger cant spin any faster because it is directly driven by the crank. So as altitude increases less and less boost will be dumped by the wastegate to keep boost at the desired level. At some altitude even with the wastegate now fully closed there wont be enough boost to maintain the desired boost and max boost pressure will begin to drop. The more altitude the more the loss. At what altitude this loss occurs in a LT4 I don't know. But I suspect at a mile high you are pretty close to the limit if not already past it.

If at this point, then your only choice is to change the pulley and spin the supercharger faster to compensate for the thinner air. That's what the racers are doing. They have calculated the pressure drop and realized they need more turns from the supercharger to produce optimum boost.

HerBlueDevil

I agree with you guys, I am pushing 10.5 Psi now after the lower pulley replacement. so Now I am going to change the upper pulley and hope it will be around 12.5 Psi. I am going to use 2.3 pulley from WeaponX. But I was told that I need to machine the supercharger so the pulley will fit.

6Speeder

Good gains. What percentage is the pulley overdriving the supercharger and which CAI?

I'm in Albuquerque, the altitude at my house is 6,000', similar to yours. I put on the Halltech CAI and a 9% overdrive pulley and gained 68 SAE RWHP/71 RWTQ over stock, no tune. My boost went up 1.5 PSI, to 10.74 peak. We also dyno'd a stock A8, results mirrored yours, about 30 SAE RWHP less than my M7 stock.

Ben@WeaponX

Correct, my 2.4 doesn't require modification but it's only .1 different than OEM. The 2.3 does require slight modification, but this is nothing new. Snout modification has been required for smaller pulleys since the LS9 and LSA engines.

Sk8Man_

Please help me to understand what is happening between "run #001" here in this dyno report and "run #002" in your first posting above?! The dates and times and your comments confuse my ignorance! Your saying that "002" was car as stock with 540HP reported, so what is "001" with 554HP reported and being run 2 minutes earlier than "002"??

What is occurring between runs "001", "002", and "004"? What happened with "003" altogether?

NicD

Huh? The ECM doesn't command the bypass valve at WOT to act as a wastegate in the traditional sense of always maintaining a set boost level. It's boost level varies directly with density altitude and from the factory never creates "excess boost", it's not a turbo setup. Pullying the blower more aggressively at altitude is typical to make up for the thinner air.

dar02081961

I was speaking of supercharger design in general.
And it seems we are in agreement.

You stated "The ECM doesn't command the bypass valve at WOT to act as a wastegate in the traditional sense of always maintaining a set boost level."
I never said it did.

I started my explanation with the question "how much excess boost the supercharger normally produces. In other words at sea level how much boost is released by the wastegate normally?"

If the answer to this question for the LT4 is NONE as you suggest, then we are in total agreement that excess boost isn’t controlled by the wastegate simply because there isn’t any.

You also state "Pullying the blower more aggressively at altitude is typical to make up for the thinner air."

Again we are in agreement as I stated "If at this point, then your only choice is to change the pulley and spin the supercharger faster to compensate for the thinner air. That's what the racers are doing. They have calculated the pressure drop and realized they need more turns from the supercharger to produce optimum boost."

I was trying to explain the principle in basic terms without getting too technical.

My point was at some point as altitude increases,max boost pressure will begin to drop on a supercharged motor.
Where this point is depends on how much excess boost the supercharger can theoretically produce at sea level.

NicD

No, we are not. These blowers don't have a wastegate, they have a bypass and it acts nothing like a wastegate.

Yes you did in non-certain words.
There is no excess boost that it normally produces that it would "wastegate" off, there is no headroom so to speak on this blower, it doesn't dump boost like a wastegate at all, there is no altitude varience from a bypass standpoint on the LT4.


It's not at some point it's at all points that boost pressure is tied to density altitude. Stop saying excess boost because it doesn't actively control max boost levels based on altitude. You are saying that the ECM or the supercharger is bypassing excess boost at sea level and there is a point that it won't do that anymore based on altitude, just stop.

Colonel

"Good gains. What percentage is the pulley overdriving the supercharger and which CAI?

According to Lingenfelter's website, their pulley is 15%.

I'm wondering how much peak power difference, if any, there is between the 9, 15, and 18% pulleys that are available. At some point of spinning the supercharger faster there will be no further gain in peak power due to heat. Where is what I'd like to know.

dar02081961

Like I said I was discussing supercharger theory in general and not discussing the LT4 specifically.

In general all compressors (turbochargers/superchargers) have a relief valves. I understand your point about the LT4's relief valve not being a wastegate. I used the term wastegate interchangeably with relief valve. I shouldn't have because you are correct in that they operate differently and wastegates are generally used on turbos or centrifugal superchargers. However they are both relief valves and both achieve the same goal which is to "relieve" or "waste" excess manifold pressure.

Again I never said the LT4 produced excess boost at WOT because I don’t know. And this is the reason I asked the question “how much boost is released by the wastegate normally?” at sea level.

Again my discussion was in general. And why I started my original post by saying “Both schools of thought are correct some of the time.” If the answer to my question is NONE then none of my discussion after that point applies simply because as you stated there is no excess boost to discuss.

However all superchargers are not perfectly matched to engine needs and some can and do produce excess boost at sea level. And in some cases designers intentionally optimize the supercharger for altitudes higher than sea level as in aircraft for example. It was for these cases the rest of my discussion was intended.

So again I was speaking in general about supercharger theory because I don’t know what altitude the LT4 supercharger was optimized for. You are saying the LT4 supercharger can’t create excess boost at WOT regardless of altitude. If that’s the case that’s fine by me.

cajunboyz

Daum, Pretty good for stok HP #'s

robbieroflcopter

Do you happen to know what the uncorrected numbers were before and after? I'm curious what we lose at altitude. I'm guessing I could throw on an 18 percent pulley without a tune to make up for the 15 percent loss of air density at our altitude.

EMINENT 1

You're not running it untuned, are you?

Is that safe to run intake and pulley without tune?