Pontiac Firebird 1967-2002 - No HP gain after costly mods. bad tune or exh?
06-07-2012, 04:22 AM
before latest mods: prc stage I heads, MS3 cam, 42lb injectors, ls6 intake, long tube headers, 3" y-pipe, stock intermidiate pipe, magnaflo muf, stock tail pipes.
today added: Fast 102 with Fast fuel rails, 102 tb, no MAF and running speed density.
Are these heartbreaking results due to a bad tune, restricted stock intermidiate pipe and tail pipes or could it be something else? This latest mod was very expensive for me to get no results. Can anyone help me figure this out?
06-07-2012, 12:38 PM
Do you have the graphs? Peak #'s honestly aren't as important as where it happens and the amount under the curve.
Did you do this on the same dyno as well?
need to see dyno sheet as you may have gain 30 under the peak which maybe huge/ plus did you use the same dyno they show different number it is just a tool/ you should of dyno it then went back and did it again on the same dyno if you did not go to the same place.
06-07-2012, 01:00 PM
Adding a fast 102 usually doesnt pick up much under peak, more top end. I would definitely add a cut out after the Y pipe, should easily pick up 15 with your setup regardless. A lot of other factors like weather, different dyno, different wheels, tires, gear and all that will effect the numbers. We need more info.
06-07-2012, 02:49 PM
Yes same tuner same dyno. Its a 6m, ford 8.8 diff and it was about 91 degrees F
06-07-2012, 02:50 PM
Ordering cut out today
06-07-2012, 03:07 PM
Who tuned it? We are saying that if you dyno'd the previous setup back in Jan @ 40 degree's, you'll see a drop to the 91 degrees run typically.
06-07-2012, 10:19 PM
That's if they aren't doing any SAE correction.
06-11-2012, 08:51 PM
Just to update, I havent been back to the dyno yet but I will post the dyno numbers as soon as I get them. I had developed an oil leak with the last dyno run and have it apart waiting on knock sensor grommets. The catch can was connected backwards also.
07-05-2012, 10:17 PM
Sorry it took so long to get back with you all. I was only able to do two pulls today and heres what I got:
It still seems like I should be doing better than this. I still dont think the Fast-102 with T/B has done anything for me except take my money. I cant figure this out. The outside temp was 99F though. I have the dyno sheet if it helps to figure this out
07-05-2012, 11:35 PM
12 hp gain is not all that bad on that set up in hot weather. The LS6 can support 400whp very easy so i dont think it was hurting you at all. Also why did you go SD so soon when the factory MAF can handle over 500 to the wheels? What size is the exhaust that runs from your Y pipe to the muffler?
07-06-2012, 12:46 AM
It has long tube headers with a 3" y-pipe into the factory intermiediate pipe where the cut-out has just been installed. I did away with the maf because it was so much smaller than the 102mm Throttle body and figured it would be a restriction.
07-06-2012, 01:17 AM
I've personally seen a friend of mine make 418 rwhp with the MS3 cam and long tube headers, still with the ls6 intake and untouched 241 heads with t56 and 10 bolt, something isn't right in your setup IMO.
What's the valvetrain consist of?
07-06-2012, 01:25 AM
yes exactly. Thats my dissapointment and I agree with you. It should be doing a lot better than this. The vavletrain consists of ls7 lifters, harden push rods, 650 dual valve springs, factory rockers.
07-06-2012, 02:32 AM
I would really like to figure out why i'm down on power but I'm out of ideas. I really dont think its the tune because this tuner does this everyday for the last seven years. And well, hes also a good friend of mine and I dont want to think its the tune. I dont know much about tuning but he says, "making HP is the easy part. Its the driveability is where it gets more difficult." Would most Tuners agree with that statement? Well one more thing. I have the factory fuel pump. Is there still enough fuel pressure for my application? I would think the Tuner would notice a fuel problem though. If anyone could help me figure this out I would be very thankfull.
07-06-2012, 02:40 AM
As long as the wideband doesn't show a difference in AFR throughout the pull it shouldn't be an issue. But to be safe have the pressure checked. His attitude sounds like its more of a street tune, which will show less than a dyno tune pretty much everytime. As far as your exhaust I guarantee it is killing you, at least get a full catback if not true duals. But even with the exhaust that setup would still respond by a large amount on the top end. I know you dont want to hear this but its the tune. There is no reason a little 224 cammed LS1 will gain around 15 peak and your setup gained the same amount
07-06-2012, 02:50 AM
Even with the cut-out you think the exhuast is still restrictive? And he does do the tune with the dyno. I should consider the tune is where most of the problem is? Thanks for your input and everyone else
07-06-2012, 04:09 AM
The Y merge is where the power is going to be, what kind of y pipe?
07-06-2012, 04:11 AM
Its a 3" Y-pipe. I think its a Headman Y-pipe
07-06-2012, 12:17 PM
I bet if you put a quality y-pipe and intermediate and back you will pick up 15-20 easily
07-06-2012, 01:11 PM
Dyno graph would help. What are you revving to? What's timing at? Unless your pump is on the way out which is always possible if its stock you have plenty of fuel with the 42#'s. One thing a lot of people dont consider now days when tuning is the E10, just a thought.
Rather than go buy a Y pipe, just pull the exhaust off and see if it picks up 20-30hp open header, then you'll know for sure. Watch the injectors while he is tuning it to see if they are going past 80%, that'll tell you if its the pump. Power is easy to make if everything works in harmony together.
07-06-2012, 09:36 PM
^^^^ He is right on.
Trouble shooting the issue vs throwing parts at it may save you a lot of money and pain in the long run.
07-07-2012, 04:33 AM
So remove the exhaust after the Y-pipe? The cut-out was installed right after the Y-pipe. Or are you saying make a run with open headers? I thought that open headers may be bad for the valves.
For your other questiions, the dyno runs are run to rev limiter at 6700rpm. I will ask him (tuner) about the other data timing, injetor % and the E10 tomarrow and post back. I scaned the dyno graph and have the file. I just have to figure out how to post it here. I will post it shortly. Thanks
ls1 1990 VN
07-07-2012, 05:36 AM
Just how much extra power do you assume you should be seeing with a 102/102 set up, 406rwhp & now 418rwhp.
It's not a major mod! just another bolt on which gives a few more HP, It's known that it's not a good $$$$ bolt on value for HP gained.
Yea you can change your Y pipe etc but that only means you are doing more bolt ons, still won't alter the fact of original HP gain with 102/102 change.
07-07-2012, 07:46 AM
The 406rwhp dyno run was the same number as before I installed the 102/102. The only reason it went to 418rwhp is because of the new installed cut-out. I'm assuming I would have the same gain with the previous LS6 intake set up. I would think even a stock original car set up would probably have the same gain. So I would think I would see atleast something better with the 102/102 set up. Ive seen other F body cars with better dyno results with less modifications.
07-07-2012, 08:53 AM
Here is the dyno graph. Sorry for the poor quality. If there is something you cant see just ask and i'll post back
ls1 1990 VN
07-07-2012, 07:15 PM
Have you had the car back on the track, assuming you do 1/4 ml the car for a before and after. How does it feel on the street now?
Don't get caught up with dyno numbers, it's how It feels and goes.
ls1 1990 VN
07-07-2012, 08:00 PM
You have this thread running in PCM diagnostic & Tuning as well as here. This thread needs to be :lock:
07-07-2012, 08:24 PM
damn those are STD numbers as well.. you running on all 8?
07-07-2012, 10:23 PM
So it looks like its pulling hard to 6200 and then something happens. Could be the tune, could be the Y pipe, could be all the fuel the pump can give, or something mechanical in the valvetrain. I'd start small and free though. Log the injectors and check fuel pressure, replace pump and/or hotwire, then run open header once thats sorted. Only thing open headers are bad for is your neighbors. Shortys may have a chance to burn up valves but not LT's
ls1 1990 VN
07-08-2012, 01:20 AM
07-08-2012, 08:41 AM
If you don't like it stay out of the thread. Your not a moderator you don't decide shit.
07-08-2012, 08:55 AM
I'm no expert at reading dynos... but it does look like the runs were consistent and the power builds pretty linear up to a point.. That's at least a good thing- whatever is the cause isn't random or intermittent.
What is your fuel pressure like? If you said something about it already- apologies for missing it.
07-09-2012, 12:41 PM
He's right though, same thread here, PCM, and in camaro section.