Yes, can anyone tell me why I have such "low" output numbers, especially when I see so many others that have what is essentually the same mods, producing 390 to 420hp/tq figures?

Are there really that many "factory freaks" manufactured by the General running around out there? Was I one of the 'unfortunate' ones to have purchased a "factory dog"?

So far, I have a 228/222 588/581 @ 114 Comp cam...LS6 (Z06 243) heads...underdrive pulley...SS Works Long tube headers...low restriction 3" mini-cats...H pipe...Z06 Ti catback exhaust...and a Blackwing intake, on an '04 Coupe with A4 tranny.

Three different Dynojets in three different states, say I am putting down 369hp and 354tq to the pavement. All three dyno operators say that is about what I should expect for my mods.

I do understand that a six speed will produce a little higher figures due to the lessor driveline loss, but THAT much of a difference?

What about the A4 vettes that are in the 400hp range with the same mods? What gives with all those 390-420 hp claims? Am I being lied to?....and if so, by whom?....the dyno ops, or those with the extraordinarily high output figures?

I'm getting so frustrated with all this stuff, I'm about ready to throw in the proverbial towel with this Vette and move on to something else. I'm tired of spending all this money, and always finding myself at or near the bottom of the figures heap.

Sorry for the rant...but this is just really getting to me.

 

My numbers on my old engine (now dead) with A4 were 420RWHP and 390RWTQ. I had AFR heads, 220-224 Comp Cam, Fast Intake and ported LS2 TB and a Haltech Trap.

So you can figure out what the differences are with your setup.....


DH

 

Are the heads LS6 heads ported/polished? If not, that could be the cause. The only other thing I can think of is the tune. I have similar mods and I am 420RWHP on an A4

 

Majik,
Just curious but would the gearing in the rear end have much of an effect? I've got a 2000 with the 6 speed and minor mods and dyno at 321hp and 335tq. I've got the 342 rear gears where the A4 guys have 273's. They usually run 10-15 hp lower than me.

Kelly

 

I asked that very question in an earlier thread, and the general concensus was that what 'differences' there are between different rear end ratios is negligable. The peak numbers will most likely come in at a higher RPM with the 2.73 gears, than say a 3.73 equipped vette, but the figures themselves should remain virtually the same.

Thanks for asking though...it was a good question.

 

No, not ported and polished...just "cleaned up" and slightly milled to ensure a true mating surface. I was told by the installer/tuner that those heads flow plenty good considering the cam I was using.

So you're suggesting that your additional 50 hp over mine is due to your having ported and polished heads of similar configuration? Is that a reasonable claim? I'm not trying to be a SA here, just trying to learn something.

 

It might not be all of it. I don't know my exact cam specs, so it may be more aggressive. It is also common for the ported/polished LS6 heads sold in the market to be milled to increase the compression ratio. The stock heads do flow well, but porting/polishing and the extra compression make a significant difference in the flow rates and combustion efficiency.

Someone else may have an opinion on the matter.

Chris

 

Hmmm, you had more air coming in.......and I would assume about the same exhaust set as mine. From that, I am to conclude that is what accounts for your additional 50hp and 40 tq? Just more air?

So what's the actual limiting factor here?.......Personally, I would say it would have been the cam......but that's apparently not it, because WITH that cam, you put some highly respectable power.

The only this left are the heads, right? Is it safe to say that I erred in having these Z06 heads put on......and that I should have either modified them or put on something different and THAT would make up for the 50 lost ponies I don't have?

I asked my tuner/installer that very same question and he told me that it would be a waste of time and money, what with the cam I have in there......that the cam would hold back whatever gains in airflow I would have benefitted from with larger flowing heads.

It seems I can never get a majority to agree on anything when it comes to these sorts of mods, (no disrespect intended to you, of course). Just making an observation.

I simply don't have the resources to continue on with all this "trial and error" sort of thing that's been going on so far. Surely SOMEONE eventually has "gotten it right", to where this info could be passed on to a dummie like me.

I realize right now, I have been 'all mouth'......now, I'm 'all ears'.....teach me what I need to know.

 

I would think your numbers are dead on. Unported LS2/6 heads are maybe worth 10-15rwhp. With stage II 5.3's, a 230/236 .570/.578 114+4 cam, and full bolt ons, I only managed 388rwhp. With a larger MAF, airbridge, and a FAST90/90 combo, I'm now at 410/390.
Then again, I ran a 11.11 with 388rwhp and 11.05 with 397rwhp. So dyno numbers really shouldn't be your biggest concern.

 

Although it might sound a little low, how does it run. Dyno numbers don't say everything.

I've got a larger cam (232/236) and M6/4:10's and I dynoed at 420, but my torque is only 358 at the rear wheels.

As soon as it cools off a little I'll see how I do in the 1/4.

Bob K.

 

I too am going the the track Saturday to see what it will do. When trying to hone my launch technique, I noticed something really strange. I started a new post here about that.

Maybe you'd like to take a look and offer an educated opinion.

As far as the dyno numbers, yeah I realize they are only good for before and after tuning purposes....but still, my numbers seem really pathetic in the shadow of some others here with about the same set-up.

Thanks for the response, for ALL the responses, for that matter. Every little bit helps.

 

An a4 will post about 3% less hp than a stick with the same mods. I think the figures are roughly 15 and 18%.

 

A couple things come to mind.

Why did you go with a reverse split cam? Most guys go with a longer duration exhaust lobe than intake.

Tune. What amount of timing advance are you running, what's your A/F, and are you getting KR?

Engine/tranny/diff temps. You want to make the run with a cool engine (160 to 190), but with the tranny and diff up to temp so the lubes are not so thick and flow better.

Good luck, hope you get some results you like

 

Trust me, it wasn't my idea. The installer decided to substitute the cam I had requested, without my prior knowledge or consent. (We) had initally agreed on a 222/228 581/588 Comp cam. I never did get a satisfactory answer as why the reverse split cam was installed in its place....except that it was also installed in his personal Z06 and made exceptional power.

I have never quite understood the logic and reasoning behind degreeing more air in to the comb chamber than is being exhausted. Makes absolutely no sense to me.

Don't know the first answer...but had two completely different tuners check it out and "said it was ok". A/F is "slightly rich" due to a tendency for this particular LS1 to predetonate on 91 oct fuel. Incidentally, it still pings under load in high ambient temps. I'm told it's to be expected with a Corvette running 10.5:1 compression. There are no indications of any knock retard throughout the power curve.

Engine usually runs from 190-201. Fans are set to come on sooner than factory settings.....still have factory stat, am going to change it to a 180. Tranny (with a new Hayden cooler) now runs 175, and up to 200 with really hard driving.

Yeah, me too. As a passing thought, I realize the 2.73 gears are still holding me back some, but I have the impression that there is quite a bit of "torque management" still at work. I can't seem to get a definitive answer from either tuner as to whether that has been disabled, or at least modified some.

I'll let y'all know how it goes at the track on Saturday. Temps are reported to be in the low to mid 80's, and of course you probably know about what kind of humidity we have here in Iowa.

 

If you run it a little cooler you MAY cut down on the pinging. Mine did. That will allow you to add more timing or lean it out a little for more power. Also, get some cold air to that blackwing by opening the foglight area. We tested my Vortex, a halltech, and a blackwing and the blackwing had the highest IAT's. On the dyno this shouldn't matter, but on the street it sure does.

Also, it's a long shot but.... have your injectors cleaned. If one is clogged it could cause the pinging by allowing that cylinder to go lean. Then the PCM will cause the rest to be fat so it gets the combined A/F it wants to see. And, of course it will reduce timing. Any of the above will reduce power.

 

What springs are you running in your 243's? If you don't have the yellow LS6 springs, or aftermarket ones, you may be getting valve float with the amount of lift your cam has.

 

Could depend on the dyno they used.... I've hear the Mustang dyno gives the lowest mumbers by quite a bit. There are newer ones which give off different results than the same model, but older. There are hydrolic ones and ones which hook to your wheel bolts, and ones with rollers, etc., etc., etc. They all produce different results? Main thing is your tuner uses the dyno machine to tune your car - the numbers are only for bragging rights. Also there is a standard dyno testing criteria which most dynos calibrate to - think it's called SAE. It's what is supposed to somewhat smooth out the rough curve of different dyno testing methods maybe your numbers weren't calibrated. Lastly (and don't ask me to explain this) I've heard of some dyno's being set for 4 wd (rather than 2wd) and that dramatically throws off the numbers - why they do it, I don't know... why they don't turn it back to 2 wd, I don't know.... why I got out of bed this morning, aw hell this could go on forever. Do you happen to know what other "proven" cars dyno'ed on the same machine you were on - that would help determine if it's you or the unit. From what you were told by the testers .... "your about where you should be"... it sorta leads one to believe they units just throw off low numbers which means your car is running fine.

On a DynaPack dyno runing short headers, 6sp, 3:42, stock LS6 heads (with upgraded springs & rods), 220/220/114 cam, I dyno'ed 378 hp & 372 torque. My cam is about as puny as you can get and still call it a mod.

I think you are correct, you should be posting better numbers. Because of the limitations of the LS6 head you probably won't see a realistic 400, but 385 - 395 rwhp I feel is the neighborhood you should be hangin in.

I'm not a mechanic and you obviously need to talk with some specialists. My gut is telling me it would be best to find out more about why your making low power before you max out your componets at the drags. If something isn't correct, now would be the best to find it and fix it.

good hunting

 

I have a 6 speed with 80k miles. Z06 CNC ported heads with dual springs, Z06 intake, Blackwing, 224/228 578/591 115 with LT's and Hi flo cats. I think you are right. Should be a bit more horsepower there.

Could be the tune or lack of ported heads with attending springs.

Good luck.

 

The heads are probably your hold up. I had a cam only LS1 and picked up 65hp with PP LS6 stage 2 heads, 30hp bolted on and 35hp more from a proper tune. So yes 50hp is possible with a better set of heads.

 

To the last 2 or 3 posters: all three dyno runs were on DynoJet units.

I went with the Comp 918 springs and chrome/moly pushrods, along with the 243 heads.

It would seem that the overall consensus now is leaning in the direction that the heads need to be reworked to improve the flow characteristics.

As far as 'stressing' the existing components, I think I've got them all pretty well "broken in" and adequately "tested". If something was going to break, it would've done it by now.

So, it's off to the races Saturday, and afterwards, see if I can get lined up somewhere and get those heads worked on.......and get some 3.15 gears put in while I'm at it.

Don't anyone be giving me grief about that now....I'm positive I don't want 3.42's. Thanks all for your help.