I had my car dynoed in Atlanta last May to give me some baseline numbers. The car had about 60k on it and still had the original plugs and wires. The mods I had at that time were as follows.

Moroso CAI
TB bypass
Airfoil
MAF ported and descreened
Flowmaster catback (American Thunder)
180* Thermostat

The numbers I got were 251rwhp/284rwtq. I did not have any O2 readings, wideband was not available. This dyno run was done in 3rd gear.

Since then I have changed the plugs and wires, added Hooker LT's, removed the cat, egr,air pump and added a cutout.

edit: I forgot to state that I have the LT4KM and UD pulley set.

The BFBA had a dyno day and I took the TA down to see the gains. These runs were done in 2nd gear. The operator was not too comfortable doing the automatic car pulls in 3rd fearing the risk of downshifting.

The first time with the cutout open and got 252.9/319.6. I think that torque number was screwy cause it did not duplicate or even come close on the other runs.

2nd run I got 254.6/287.4 @ peak hp my AFR was 12.8. This was also with the cutout open.

3rd run, I closed the cutout and gave that a try. I got 253.5/284.4. Hmmm no change. I guess the old exhaust is pretty free, huh? The AFR looks to be about 12.8-12.9.

I was data logging with DataMaster. I got two runs in one record, cause I really don't know how to use it yet. I am getting some really crazy readings on the BPW and the INJ DC. I also got 5* of knock retard.

It looks like I have some work to do. I think that my knock is coming from my y-pipe so I am going to try insulating it first and see what happens.

I was really hoping for SOME improvement, but NO improvement is confusing.

We did see some real gains, 7-10 hp on the LS1's by removing the MAF screen. We also saw the K&N filters cause some lower HP numbers vs. some stock filters.

If anybody wants to, or will look at the DataMaster file I will be glad to send it to ya. I will take all the help I can get.

I do now have TunerCat, so I can make programming changes where I need to. The problem with this is, I have no idea what to change.

Any ideas?

 

I would have paid money to see you dyno WITH a cat. You might have been surprised.

 

Ed, why?

 

With long tubes and no cats you have zero back pressure. This is further exemplified by the fact your cutout had no HP difference. Have you ever heard, "a little back pressure is good"? You need some 'resistance' on the exhaust side for optimal filling of the combustion chamber. Bolt-up a cat one of these days just for snicks if you can (I should know better since you have LTs).

 

Ed, yes I have heard that "a little back pressure is good". I did not know what to expect from these mods. Good thing I have a dyno close, huh?

Got any other ideas on adding a little backpressure other than a cat? I have no room for it under there. Maybe a different type muffler?

What do you mean by "(I should know better since you have LTs)."??

 

i cant contribute any explanation as far as why there was no gain...

but

a buddy of mine did 27x hp/30x tq on an otherwise bone stock 95 m6 Formula w/ Hooker LTs, a 2.5" ypipe (no cats) blowing out a cutout on a stock cat back.

back pressure didn't seem to hurt my friend...

my $.35

 

uhh is it just me or did anyone else notice 5* of knock retard
that would do it

 

damn....didn't see that...

guess i should start reading more closely

 

Trey, that is what I was thinking. But being VERY new to this whole tuning thing I wanted some opinions. What are some ballpark gains do you whink I will see when I get the knock fixed? Also, what about this whole backpressure thing? Should I add some or not?

 

I'd get an LT4 KM and it SHOULD fix it seeing how u got the knock after headers- it might be false (probobly)

FWIW with backpressure i ran 13.2 106 with long tubes, no cat, 3'' y pipe and no cat

i took off the muffler and ran a 13.6 a few times
compare your graphs-
did you lose any power down low? if so then yes a little more wont hurt
if not, your kosher

 

this is probably obvious but you must have a 1:1 gear ratio when using the dyno to get the correct figures. i know on a 6 spd.... that gear is 4th. if you used 3rd on one pull and 2nd on the other then we have found your problem.

i dont think 5 degrees of knock retard will rob you of what should be an easy 30 rwhp gain. but knock retard is bad so fix that and see what happens. didnt you feel a good power increase in your seat with the headers?

 

if anything the 2nd gear would pull more
i'm sure they enter it into the computer and adjust for it though

 

Actually, dynoing in a lower gear will yield lower hp numbers.

 

i'm just going on my first instinct-
why would it ?

you have more thrust in 2nd gear???

besides you enter the info in the computer for the gearing dont you?

 

Oops, I forgot I already have the LT4KM. I can only imagine what my reard would be w/o it, probably the full 12* in the table. I also have UD pulley in the crank and an OD pulley on the alternator.

My gears in 3rd are 1:1, and if I remember correctly that is what was being said that "you want to pull in". So I am assuming (we know what that will get me ) that the computer is set to calculate at a 1:1 ratio. If I pulled in 2nd, I am not at 1:1 so maybe the numbers are wrong. The dyno operator was afraid of downshifting on the dyno.

I did a few runs on the interstate last night to check what I saw in the setup tables. My car is set to kickdown from 3rd to 2nd at less that 67mph. In third @ 3k the car is above that and does not kickdown. So when I return I will pull in 3rd, tell him to go from 3Krpm up and see what the results are.

I know this question should probably be in the programming section, but...

Do you guys have any suggestions as to any programming changes that I need to make? Other that the fans and idle speed. I am going to bring up my idle because of the UD pulleys, they cause my voltage to drop at warm idle.