Just got back from my dyno session. Below is the chart from my baseline and the new setup. Note that I have also included the AFR so you can see that the tune is conservative at the high end at just about 12:1. The tuner, Slowhawk (Don), likes to keep it this way for driving on the street and because the car will lean a bit from the dyno anyhow. It is a smidge leaner than the stock tune up to about 6,000 RPM where it is the same. I picked up just under 25 HP at the peak and am happy with the results. I was asked what I was hoping for when I went in and I said I would be happy at 330 HP. We were over that with a leaner tune on an earlier run, but tuned it back a smidge for street driving. Don also showed me a back to back run with an f-body that had Random Tech cats and then had them removed. The cats cost a solid 10 HP, so if I remove the cats I could be at around 340 HP. All in all it was a fun day and I thank Don for his time and his expertise. I highly recommend him for tuning if you are anywhere in the New England area (or farther away ). Here is the plot.

 

How much total for 25hp?

 

Looks like 24.1 RWHP and 17.3 ft lbs of torque. I expected to see more from the descriptions of the merits of the Tri Y design which were pointed out to us.

Thats about the same HP gain that people get with the other header brands out there. But maybe even somewhat low on the torque. But if you are happy, then thats all that matters.

http://forums.corvetteforum.com/showthread.php?t=928933

 

Why was this run started so late compared to the last one? I would like to see the graph with lets say, 13.1 air/fuel.

 

I didn't keep the 13:1 graph because it doesn't represent how the car will hit the street. You couldn't run it like that on the street. I would only caution when making comparisons, that if the AFR isn't on the graph you don't know how it was tuned. All the information is here.

 

I understand that. I just wanted to see the graph. Why was the run started so late? I can't get a good idea of low end torque with this graph.

 

To be honest with you, not sure. He was making runs in pairs, and typically the second run of each pair was made with the car already in fourth gear. He was checking AFR and other parameters, likely not the best scenario to get a bottom to top curve.

 

Ok. I think the numbers look good considering the conservative tune. QTP makes a quality header.

 

I think they came out well also. These are not bragging numbers, but then again I have a tune that I am totally comfortable with as I hope to drive the car cross-country next year. The other thing that I was shown while at the tuners was an f-body with headers and with and without a Random Tech cat setup. Removing the cats was worth 10 HP. So the way I look at, I "could" have been around 340 HP without the cats but elected to go with them.

 

Yeah. I guess thats one way of looking at it.

 

Hi Bob,

Congratulations

LG

 

Lou,

Can't comment on the above curve, but if you refer to LS1HOWTO.COM, my gains are on par with what they had gotten with the LG's from their installation. I do see the dip in my curve, and my tuner brought up other stock curves from 2002 models. That dip was evident in the other curves as well so I don't believe it was just my car or bad gas. As a matter of fact, the stock curves almost laid on top of each other dip and all indicating that the factory tune may have had some very aggressive tuning. As I stated earlier in the thread, we did have some higher curves, but pulled it back with the AFR. I also believe he was a little less agressive with the timing tables in the lower RPM but am not sure on that. I think the cat loss difference is possibly due to your 3" cat vs. the 2-3/4" cat that I am using, but in speaking with Randon Tech technical support, they told me the 3" system doesn't mate with the exhaust I have.

I am also curious as to whether I would have had more of a gain or less of a gain with the elimination of the base knock retard as pulling the advance would have also decreased the curve as well so I may have actually been lower on my baseline across the lower RPM's. The stock program seemed to be very aggressive at these lower RPM's. As I remember, there was a TSB out on this for the 2002 and the people who got the knock removed (it was audible) also complained later on the loss of power. I guess what I am trying to point out is that the perceived increases in power that were acheived could have been larger had I had the TSB completed with the newer less aggressive timing curve from GM and also leaned the AFR on the dyno. I chose not to do either since I really don't like the dealer touching my car and I wanted a very conservative tune. I can tell you the car pulls much harder and smoother and the throttle response is much crisper.

I don't want to appear to be bashing the LG's, on the contrary they were in my final two for headers. But there are so many factors in the curves that any car finally ends up with, both baseline and final, that direct comparisons between two different cars are very hard to do. I have also found threads on several manufacturers headers where people only got a few HP with the headers and others using the exact same headers had very good gains. What I have tried to put forward in this thread is all of the technical information that I have on my before and after dyno curves, the installation and the approach that was taken.

 

I have an old LGM printout from dyno runs done 6/19/03 (old, I know) on an unknown C5 with "Vortex and Air Bridge" and shows pictures of the off-road system, therefore if you assume the dyno runs were done without cats, you could subtract 5 HP from the following LGM numbers. Before and after results were both with the vortex and air bridge. Anyway, The LGM numbers are as follows:
Before Headers - Max. HP = 312.3 Max. TQ = 319.5
After Headers = Max. HP = 333.9 Max. TQ = 347

These QTP Numbers are similar, HP = 329 and TQ = 343

The A/F on the LGM at peak is noted as 13.5 on the chart.

To be fair, I don't know what model LS1 the LGM's were tested on, but the numbers look "more real" than the dyno chart shown above (what's with the peak HP of only 278???).

What I found interesting were the curves after the peak HP/TQ RPMs, where most headers start "pinching" in on the curves, i.e. the % difference between stock manifold and header start dropping. The QTP numbers don't drop as quickly as the LGM numbers. This didn't surprise me considering the apparent 'interference' type design of the Tri-Y headers. They don't tend to exhibit a "tuned" range as much as 'independence' designs which try to take advantage of the sound waves in the exhaust and "tune" the header to a certain, small RPM range, which results (if the header is designed correctly) in higher peak numbers than the Tri-Y.

I've compared the LG and QTP curves posted in various places and it appears, when the numbers are transferred to a spreadsheet, that the QTP sustain the torque longer (to a higher RPM), but not by much. This is reflected in the "peakier" graph of the LGM.

Vettenuts, looks like you made a good choice to me! Wouldn't it be great if it were easier to decide on which headers to go with

Congratulations with the good results and enjoy them!!! I envy you at the moment.

BTW, have you noticed any driving difference as a result of the tunnel plate install?



TC

 

Yes, the tunnel plate was immediately noticable even on the highway. I was so caught up in the headers I forgot to mention it. It was very easy to install, but tightening all those fasteners with a torque wrench got old in a hurry. Not sure what others are using for a torque values as I have read of broken bolts, but the service manual stipulates 89 in-lb for installation.

All in all, I am very pleased with the total outcome. I have a stiffer chassis that hopefully will help with heat (although its cold here now so this will have to wait several months to confirm), I shed 20 lbs. from the car and I picked up a decent HP gain. This is addictive though as I am now reading the manual on how to change the cam. Someone help me

 

I can buy you a power ball ticket....will that help

Looks like the only difference between you and I at this point is funds and available time. You seem to be going down the same road I'm planning, i.e., optimize the stock vehicle without increasing the HP so much that the rest of the driveline must be beefed up. The poor A4 just can't handle too much!

Looks like it'll be a year b4 I get around to my headers, unless someone builds an equal-length header with 1-5/8" primaries that are 36" long with a 2.5" collector, fourteen inches long, dumping to an x-pipe and then Random cats. Yeah, that'll happen..... Anyone got a cheap MIG welder for sale?

 

I also saw that dip in the before graph. It does not appear in the after graph.

Lou, in your above post are you saying that all of his 24.1 RWHP 17.3 ft/lbs of torque gain didn't come as a result of the headers.

But that some of that 24.1 RWHP 17.3 ft/ lbs of torque gain, maybe as much as half of it, came simply as a result of eliminating a pre existing KR in going from the baseline tune with his stock manifolds to the final tune?

Thats pretty "profound" if that is in fact what happened.

 

Fri 11-12-04

Hi Bob...

Welcome to the QTP club! ...... I see the "urge" got the better of you, as it did me!
I hope my previous reply emails enabled you to make an informed decision, based on the conservative tune I think you can be quite happy with the numbers you got.....

No matter what "set-up" you run, the "fun factor" is what it`s all about,
enjoy!

R.P..

 

Hey Vettenuts, I don't see what the fuss is about, I would think that a 25 HP increase from just header should be right on. I went back and found the site where LAPD did the test for the GHL's and with the stock Z06 they had an increase of 15 HP before they did any mods. What kind of mods have you done to your vert? Can you really tell a big difference right from the get go and through the gears or do you have to get some RPM's up before you feel things kicking in. By the way I noticed in the LAPD test threads that you were showing some interst in the GHL headers, it looks like you have been doing your homework. Bottom line no BS, if you had to do it again would you still go with QTP Tri-Y's

 

Roho,

Very hard to describe but I will try. I am very pleased with the results and would buy them again. When you look at the whole picture, stainless steel, mates to a known high quality pipe/cat system (Random Tech) and the ease of installation I think its a great system. What is hard to describe is the throttle response, even at idle. There seemed to be a lag in the motor before that I always attributed to the fly by wire throttle, but now the motor absolutely "snaps" when you blip the throttle. Even when you start it, it seems to "twist" the car like a big block. Again hard to describe, you really need to be there. A friend who came with me said he noticed right away, but as you drive the car a few times you tend to forget what it was like before. I do have more power all the way the RPM range and now if you step on it while rolling (say 10 MPH) the traction control comes on Never did that before. I took my daughter for a ride and on the highway entrance ramp from a rolling start put about 35 feet of rubber on the ground. She went back later and showed some friends You have to realize that these headers have more welds than others due to the design and the need to merge together the 4 pipes to 2 pipes then to one final pipe. The O2 sensors in the rear fall right into their old position and the wires are run the same way as stock. Perfect fit. The front O2 sensors are very close to stock and no extensions are required. Again, perfect fit. The tabs lined up to the bracket on the bell housing, the left one was right on and I just screwed in the bolt. The right one was off by about 1/4 bolt diameter and just a little nudge while putting in the bolt and it went right in. I did not have to heat them a few cycles and then try again or use pry bars to get in the bolts. If you ever need to change the front O2 sensors it can be done without removing anything. Just unplug the O2 (although this is a feat even with the stock setup ) and spin it out and put in the new one. As for the tunnel plate and access for say a clutch change, only the mid-section would require removal, not the headers, just like stock. So in the end, I think there are hidden advantages to this system (not sure about others) that go beyond the HP increases.
Also, make sure you look at the low end of my plot, the timing curve in my particular car was very aggressive and lead to knock in the baseline curve. I am in the process right now of digitizing my curves so I can plot them against an 04 that doesn't exhibit this same timing to knock to see what kind of gains would have been realized in the lower end if I had not had a car with such aggressive timing down low. I would have ended up in the same place, but the "perceived" gain would have been higher. Also, look at the power up top and how the curve flattens from about 5,100 RPM to redline. It was flatter maybe even increasing in an earlier run before the final AFR was set to richen it up a tad. Again, Slowhawk is very conservative with his tunes and that is exactly what I wanted so I don't have to worry in the future about the motor. These curves, in my opinion, show a very honest gain represesnting what the average Vette owner should get when he installs this system. I tried not to develop a dyno queen to get better numbers.

 

Vettenuts,
I have a 2004 mn6 vert, and now I have the header bug. I've already done Corsa Indy's, an x-pipe, and the new Callaway CAI. I think Santa is thinking of headers for Christmas.

I've followed this thread from the beginning, and it sounds like you are happy with the QTP's. I also like your conservative but careful approach to tuning. These are great cars, and I only want to make a good thing better.

Is there any less ground clearance with your QTP's than with stock headers? On my car, the Corsa's were great, and then with the CAI, I got more power, but a little pre-ignition ping and lower mileage. So as my addiction has progressed to the header stage, I'm wondering if a careful, conservative tune might help.

I live in Connecticut, so a run up to RI for a dyno tune would be great fun. Otherwise, do you, or anyone else, know of a good shop in Ct?

Thanks,

HHNTR111