Author Topic: Can a wrong exhaust setup ruin ls1 power?  (Read 166 times)

boeing9999

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Can a wrong exhaust setup ruin ls1 power?
« on: July 09, 2019, 08:58:22 AM »
???????Hello guys!
I have a 1979 T/A with a stock 2001 LS1 (LS6 intake) and a T56. Exhaust setup is Hooker mid-length BlackHeart 2.5' headers, true duals (no x- or h- pipe crossing, just 2 separate pipes of 2.5' diameter, same width as headers ), Glasspacks (with shells/openings directed facing opposite the engine / not blocking exhaust flow).
As far as I know a stock LS1 should be 305-350 hp. The engine swap went on for 1.5 years and I only started to test everything running a month ago when all finished, and my sensations tell me that the car isn't running as fast as it should. Especially in the low RPMs in 1-3 gears. Until you reach around 3500-4000 RPMs in any gear, you don't feel much acceleration, it feels like turbo lag. I can only compare with my Mitsubishi 3000GT VR-4 (3 liter twin turbo, 286HP), and that car accelerates faster (you feel a kick in the back), whereas my LS1 car raises hell with the extremely loud exhaust, but the dynamics don't match the noise it makes. Strangely, acceleration is best felt in 3rd gear after 3000 rpm.. :?

Question: given that my LS1 is stock (except the mid length headers and ls6 intake), can the lack of power and low-end torque be due to my use of 2.5' pipes for true duals exhaust? As far as I've read, 2 separate 2.5' pipes should be good for a 1000hp setup, and maybe I'm running the pipes which are too wide for my engine and I'm not creating enough tension/ back pressure in the exhaust system?
Would appreciate any advice on how to finally start to feel the much awaited LS1 might and glory!











ryeguy2006a

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Re: Can a wrong exhaust setup ruin ls1 power?
« Reply #1 on: July 09, 2019, 11:05:50 AM »
???????Hello guys!
I have a 1979 T/A with a stock 2001 LS1 (LS6 intake) and a T56. Exhaust setup is Hooker mid-length BlackHeart 2.5' headers, true duals (no x- or h- pipe crossing, just 2 separate pipes of 2.5' diameter, same width as headers ), Glasspacks (with shells/openings directed facing opposite the engine / not blocking exhaust flow).
As far as I know a stock LS1 should be 305-350 hp. The engine swap went on for 1.5 years and I only started to test everything running a month ago when all finished, and my sensations tell me that the car isn't running as fast as it should. Especially in the low RPMs in 1-3 gears. Until you reach around 3500-4000 RPMs in any gear, you don't feel much acceleration, it feels like turbo lag. I can only compare with my Mitsubishi 3000GT VR-4 (3 liter twin turbo, 286HP), and that car accelerates faster (you feel a kick in the back), whereas my LS1 car raises hell with the extremely loud exhaust, but the dynamics don't match the noise it makes. Strangely, acceleration is best felt in 3rd gear after 3000 rpm.. :?

Question: given that my LS1 is stock (except the mid length headers and ls6 intake), can the lack of power and low-end torque be due to my use of 2.5' pipes for true duals exhaust? As far as I've read, 2 separate 2.5' pipes should be good for a 1000hp setup, and maybe I'm running the pipes which are too wide for my engine and I'm not creating enough tension/ back pressure in the exhaust system?
Would appreciate any advice on how to finally start to feel the much awaited LS1 might and glory!





That should be more than enough exhaust to feed a stock LS1. With a 6 speed, you should be able to feel the acceleration from about 2k up to redline. Mine pulls so hard sometimes I accidentally bounce if off the rev limiter.

Couple questions, one is where did in the pipe did you mount the O2 sensor? What are your fuel trims LT and ST? This looks like there are several pin holes that could be allowing the motor to get a false O2 sensor reading which would make the car run poorly.



Another thing is who did your tuning? It sounds like it could also be a tuning issue with possibly a setting that was missed when it was flashed to stand alone.

Is it throwing any engine codes?

1976 Trans Am LS1, 6 speed, C5 12.8" Brakes, LS1 rear 12" brakes, 17" Aluminum Rims, and much more...SOLD
My Build: http://transamcountry.com/community/index.php?topic=24465.0

New project: 1968 Camaro with 6?.?0?  5.3 w/ Z06 cam/T56
http://transamcountry.com/community/index.php?topic=74591.0

Casey

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Re: Can a wrong exhaust setup ruin ls1 power?
« Reply #2 on: July 09, 2019, 01:33:08 PM »
Those louvered core glasspacks kill power as does having true duals without a crossover, but not to the degree you're experiencing it.  I agree with rye, sounds like a tuning issue and or sensor/ECU related.  Though a simple thought, how old is the fuel in it and what octane?  Should be 91/93 and if it were sitting during the swap it's probably not any good.  Which if you've filled it up since on 91/93 that should be ok.
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NOT A TA

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Re: Can a wrong exhaust setup ruin ls1 power?
« Reply #3 on: July 09, 2019, 06:52:45 PM »
Did you do some calculations before the swap to decide what trans gears, rear end gears,  and tire diameter would give you the results you wanted with the basically stock LS engine?
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boeing9999

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Re: Can a wrong exhaust setup ruin ls1 power?
« Reply #4 on: July 10, 2019, 08:31:51 AM »
That should be more than enough exhaust to feed a stock LS1. With a 6 speed, you should be able to feel the acceleration from about 2k up to redline. Mine pulls so hard sometimes I accidentally bounce if off the rev limiter.

Couple questions, one is where did in the pipe did you mount the O2 sensor? What are your fuel trims LT and ST? This looks like there are several pin holes that could be allowing the motor to get a false O2 sensor reading which would make the car run poorly.

Another thing is who did your tuning? It sounds like it could also be a tuning issue with possibly a setting that was missed when it was flashed to stand alone.

Is it throwing any engine codes?

Hi! Thank you for your replies!
Here's where my O2 sensors are located.


Fuel trims - don't have an idea at the moment, we haven't connected to the ECU yet. Catalytic converters were cut out, and the corresponding changes were applied in the ECU of the previous (donor) car. The shop recently received HP Tuners device, I hope this can do it. Currently the car should be running with settings of the donor car (2001 Trans AM).

Those louvered core glasspacks kill power as does having true duals without a crossover, but not to the degree you're experiencing it.  I agree with rye, sounds like a tuning issue and or sensor/ECU related.  Though a simple thought, how old is the fuel in it and what octane?  Should be 91/93 and if it were sitting during the swap it's probably not any good.  Which if you've filled it up since on 91/93 that should be ok.
I run 95 gas (we don't have 91-93 here). The fuel is fresh, therefore loss of power shouldn't be due to old fuel.

Did you do some calculations before the swap to decide what trans gears, rear end gears,  and tire diameter would give you the results you wanted with the basically stock LS engine?
Current trans gears and rear end gears should be identical to that of TransAM 4th gen (I had a custom rear end setting the way I bought it), so all in all the picture should be like this.
As for the wheels, they're just 5% bigger, than stock 4th gen: my 685mm (285/40/18 in the rear) vs 4th gen's 652mm (275/40/17).

As far as I can understand, my exhaust isn't the reason for slow acceleration... I'm planning to put straight-through mufflers and bring it out of the back of the car (currently running side pipes). Maybe will add an x-pipe later. Now the car sounds like two Harley Davidson bikes rolling together.

Ok, maybe it's sensors or ECU setup, maybe it's spark plugs, maybe it's ?logged injectors. I'll start my quest to sense the power of much praised LS1, which took so much time and money to swap in..
By the way, is the stock ECU well tunable? Or does it make more sense to save money for something like AEM?

Re: Can a wrong exhaust setup ruin ls1 power?
« Reply #4 on: July 10, 2019, 08:31:51 AM »

Casey

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Re: Can a wrong exhaust setup ruin ls1 power?
« Reply #5 on: July 10, 2019, 01:17:14 PM »
The stock ECU is perfectly fine for use with a stock or mostly stock motor, any tuning shop worth their salt can handle tuning a LS series engine.  Another simple thought, have you checked to make sure the throttle is opening all the way and that the cable isn't in need of adjustment?  Outside of that really won't know until you're hooked up to the ECU and can see what's going on.  Knock sensors failing on the LS1 is common, so if those weren't replaced any time soon it's possible that's the issue.
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ryeguy2006a

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Re: Can a wrong exhaust setup ruin ls1 power?
« Reply #6 on: July 12, 2019, 06:18:43 AM »
The welds on the o2 bung look good and although not the most ideal location for the o2, that shouldn't be causing the issue you describe. It is typically recommended that the sensor be located on the top half of the exhaust a few inches past the collector to avoid condensation which can ruin the sensors. Also keep in mind that even a pin hole in the weld can cause the o2 sensor to give erratic readings.

I'm curious how does the car drive when it's cold? If it does it when the motor is cold, you can rule out any o2 sensors since they only come on in closed loop. When the car is in open loop the car will rely on the internal VE tables to control fueling.

My guess is that when you plug in the tuner or code reader that you'll have codes and one will be causing the car to be in a "limp mode". It could be almost anything really. Bad IAT, MAF, O2, and etc. Check for vacuum leaks too.

Casey brought up a good point on the throttle cable. Yours truly found out recently that my throttle cable was too long causing my Camaro to only have 61% throttle when it was on the floor. A new cable fixed my issue.

If your tuner is just getting the HP tuners program and is having trouble with it, send me a PM. I have several base tunes on my laptop that I've done for people over the years and I can help you out.

1976 Trans Am LS1, 6 speed, C5 12.8" Brakes, LS1 rear 12" brakes, 17" Aluminum Rims, and much more...SOLD
My Build: http://transamcountry.com/community/index.php?topic=24465.0

New project: 1968 Camaro with 6?.?0?  5.3 w/ Z06 cam/T56
http://transamcountry.com/community/index.php?topic=74591.0

70_71_78

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Re: Can a wrong exhaust setup ruin ls1 power?
« Reply #7 on: July 12, 2019, 12:16:23 PM »
I see several issues here. Is the exhaust pipe really inserted into the inside of the header collector, as it looks like in the photo of the O2 location? Why? You need the best flow possible there and that is not helping. Can't be helping O2 accuracy. It also looks like there is a flexible section after the turn down. Why? Those are for transverse mount engines if FWD or transverse AWD application, they are not so good for flow. I have never had a RWD longitudinal mount require a flex, nor have the exhaust system on them been a problem. I too suspect that the tune may not be correct.

boeing9999

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Re: Can a wrong exhaust setup ruin ls1 power?
« Reply #8 on: July 12, 2019, 02:44:17 PM »
Another simple thought, have you checked to make sure the throttle is opening all the way and that the cable isn't in need of adjustment? 
Thank you, will check, yet probably it should be ok. My mechanic did LS swaps for 2nd gens previously and should've got this right.


I'm curious how does the car drive when it's cold? If it does it when the motor is cold, you can rule out any o2 sensors since they only come on in closed loop. When the car is in open loop the car will rely on the internal VE tables to control fueling.

My guess is that when you plug in the tuner or code reader that you'll have codes and one will be causing the car to be in a "limp mode". It could be almost anything really. Bad IAT, MAF, O2, and etc. Check for vacuum leaks too.

Casey brought up a good point on the throttle cable. Yours truly found out recently that my throttle cable was too long causing my Camaro to only have 61% throttle when it was on the floor. A new cable fixed my issue.

If your tuner is just getting the HP tuners program and is having trouble with it, send me a PM. I have several base tunes on my laptop that I've done for people over the years and I can help you out.

The acceleration is same when the car is cold( I'm very looking forward to when we'll be able to plug the car to the HP tuners and see what's happening. All in all, it isn't disasterously slow, - it roars and does wicked burnouts and doughnuts. But just as a gauge of power, compared to a fresh merc e400d, which was simply accelerating from standstill on a highway (we weren't even racing) left me in the back easily by around 2/3 of a body when we reached 80km/h. Thank you very much for the possibilty to reach you regarding available tunes - I'll keep this in mind!

I see several issues here. Is the exhaust pipe really inserted into the inside of the header collector, as it looks like in the photo of the O2 location? Why? You need the best flow possible there and that is not helping. Can't be helping O2 accuracy. It also looks like there is a flexible section after the turn down. Why? Those are for transverse mount engines if FWD or transverse AWD application, they are not so good for flow. I have never had a RWD longitudinal mount require a flex, nor have the exhaust system on them been a problem. I too suspect that the tune may not be correct.

Exhaust pipe isn't inserted like this now, it was just a part-time solution to travel to the other garage and avoid spitting fire on the asphalt along the way with open headers)
Regarding the flexible section, this is new to me, I'll raise this question with another exhaust shop next week. At the moment what I'm thinking about is adding pass-through mufflers in the back. If it'll be too loud again, I plan to add a x-pipe crossover - maybe it should smoothen the sound.

Re: Can a wrong exhaust setup ruin ls1 power?
« Reply #8 on: July 12, 2019, 02:44:17 PM »
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