Alright I had the car dynoed yesterday at 21st Century Muscle cars. Great bunch of guys over there and I am very confident in the tune so lets rule that out now.

I installed MTI's Stage 2E heads with an X1 (230/228 .591/.571 112)cam on my 99 over the Xmas holidays. I also added and LS6 intake manifold and Under drive pulley.

Before I did the heads and cam I had these mods: Vortex air box, FLP Headers, Hi-flow cats, x-pipe, B&B Bullets. The car put down 325rwhp/330tq. I was pretty happy with those numbers and those mods.

Yesterday with the H/C, new intake manifold and under drive pullies I put down 405 rwhp/375 tq. Now I was seriously expecting more like 425-440 hp and close to 400 tq. Mind you I was very dissapointed. The 21MC guys did everything to try and make me happier with dyno tricks and all but nothing.

So we did a leak down test. It was between 8-10% on each cylinder which the guys said was acceptable and not the source of any hp loss. Spark plugs and wires are fine. I do have the stock throttle body, maf, and air bridge but we all know that isnt work 20 rwhp.

So what is the deal...? Anyone else having the same problem? The car is great right now and I am enjoying it but I really feel dissapointed. Any help is greatly appreciated.

 

Well, as far as I know, all dynos are differnet. there can be many factors that give the end result. first thing id try is to get a 2nd opinion on another dyno. that would help confirm numbers. whats your a/f at wot?

But i wouldnt dwell on dyno numbers anyway. real measurement of performance can be obtained at a track. pay attention at the mph when going through the traps. that is key info on the potential of your ride. best of all, ask yourself, how does it perform on the street? you should be able to tell if the car is not running right.

fyi- I beat 2 cars so far that dynoed higher than me. dynos are tuning tools.

 

how did you choose the specs of your cam because they look unordinary for your setup?

 

Thanks for the replies so far. I am happy as I said and I will definetly try some other dynos to be sure. I wont be at the track anytime soon... stock clutch owns me. But when I do i can actually see how the car stands.

The cam is MTI's X1 cam which is pretty popular. Its reverse split which is supposed to be better for NA applications which I plan to be for now. This is at least what I have been told.

As for the hp increase... everybody else i have talked to that have this exact heads and cam (different headers and exhaust but that is marginal in my mind as most i have talked to had TPIS) have put down at least 425rwhp.

MTI has even said that they average between 415 and 440 with this setup. So I guess my question is more is there anything wrong with my setup. Maybe I didnt tighten a rocker tight enough or things like that that are small but could be the cause of the problem. I double checked every bolt mind you but there is always a chance.

Thanks again

 

There's always the chance that nothings wrong, and that's what your engine's going to put out with those mods. As there are cars that are freaks and dyno higher than usual, there are also cars that are the opposite.

Dyno's don't win races, drivers do.

 

Couldnt put it better myself... I will wait for the morning crowds responses but i see that the consensus so far is to not doubt my baby.

 

We take it personally when you doubt a Vette's abilities, even if it's yours..... . . .

 

I only dynoed 388rwhp and ran 11.11 @ 121, so don't feel so bad.

 

I have an MTI package also and was quoted slightly less than your were. No I did not hit the numbers quoted...

 

I see your , and I raise you a .........

 

Point Proven by Face .

 

i would stay away from reverse split on the ls1. they like a cam with more exhaust duration(so does NOS). your just the opposite. if i were you i check out ls1tech.com also. Did you check your quench?-you have to measure the pistons out of the hole-then see what thickness gasket you'll need. optimun quench is .035 to .040, are the heads milled? did you degree the cam? did you port match the intake?all this stuff adds up, trust me

 

Your numbers are right on. You were expecting too much. Your before numbers are low. 325hp with headers, hi-flow cats and intake. Maybe it's the headers. For example I dyno'ed 340 with a blackwing and Kooks headers and x-pipe with hi-flow cats. Then with the same heads you have, UD pulley and the slightly smaller C2 cam did 417hp. So my increase was 77hp and yours was 80hp. Damn I should really be pissed, I'm not. If you want BIG numbers you need a BIG cam.

 

See my MTI mods/dyno as a frame of reference.

 

My thoughts exactly. WHy would you choose more duration and life for the intake valves when they are already bigger than the exhaust? Ya gotta be able to get out what you took in before you can take in a new charge.

Just my thoughts

 

All that was said above...

One thing I noticed though was that your pre numbers seemed low (to me anyway). My '01 made those numbers with just a Vortex and B&B PRTs, and you have headers and high flow cats. (dyno'd at Speedworks in Lewisville).

It seems to me like the gain you got was good, to me the initial # seemed low. (I'm no expert)

 

how about your injectors, are they stock?
didn't the '99 come with 26lb injectors.
the tuning should show the duty cycle of the injectors ask the tuner to check this out.
I am not familiar with the heads (2e) and i did not see a dyno posted what does the curve look like?
are the springs floating at high rpms costing you power.
these items would not be noticed at daily driving.
just some things to look at. yes I agree that the dyno does not tell all
but it is nice to see the numbers you were expecting.

 

Nowhere do I see if you have an A4 or an M6. That would also be a factor to consider when tuners post expected numbers. The higher numbers are usually as a result of less drivetrain loss through the M6. My '99 A4 dynoed at 278 RWHP before modding so I'm am thrilled to have 405 RWHP and 385 RWTQ currently with a 4+ year old mild heads/cam package & 3.90 gears. If yours is an A4 I would say that you are right on, if not you just may have to dial her in a little bit more.

 

Try to look at the numbers as tuning tool. Don't compare numbers to other tests, dyno numbers can vary greatly with changes in your choice of tires, gears,weather conditions or sacrificing your drivability via the tuning to obtain a specific number.

 

My car has a similar set up to yours prior to the heads/cam install you got. My car put down 337hp/341 tq at Speedworks on their dyno. A year or so later at 21st Century my car only put down low 320s for both hp and tq on their dyno. I haven't changed anything on the car I guess just different days on different dynos. I also have LS1 edit and I did notice the air/fuel ratio wasn't as optimal as it was before when it was dynoed at Speedworks.