Sluggish/Slower Coyote after Longtubes

Brianh922 · Jun 20, 2018

Nuked said:
I ordered a set of long tubes so hopefully have some data to compare in a week or two. 3lb/min gain from long tubes is about right, but I agree the 42lb/min base was on the lower side. The lb/min can vary though based on the tune and fuel trims etc. Assuming the tune was the same from stock manifolds to headers, the 3lb/min makes sense.

Yup no tune change. Just the headers. I have a dyno appointment Saturday to confirm everything is working as it should be. I'll report back with numbers. As for the low lb/min on the stock headers I have no clue but the car felt great then.

markmurfie · Jun 23, 2018

Do you have a BAP? If not add one, or buy the DW400, and still add a BAP.

I took your log and did some math in excel and reuploaded it to my datazap.
First I thought clutch slip, but nope your RPM to OSS indicate no problem with clutch or transmission.
I notice your load is slightly low from what I would expect. I suspect your fuel pump is maxed out.
The way I check this is I take your load as a fraction and through some math convert it to a rough MAF value. Then compare what your MAF sensor says and what the ECU is saying from load. Usually they are dead on, except in transients, unless you have a fuel issue that was compensated for.

From the picture you can see MAF from load is lower than than your MAF sensor. The ECU is compensating for a lack of fuel rail pressure relative to its inferred pressure tables, my guess. Then again its through out the entire range, so it could just be a vacuum leak.

Oh and why is this hurting performance? The car is thinking its moving more air than it really is, so everything is setup for that airflow instead of the actual airflow. Your KR slowly made its way to 8*, this is what the stock tune does. Get that down to 2-3* and having all the timing available right a way makes a big difference in the way the car feels.

Nuked · Jun 23, 2018

Good stuff as always Mark

Brianh922 · Jun 23, 2018

markmurfie said:
Do you have a BAP? If not add one, or buy the DW400, and still add a BAP.

I took your log and did some math in excel and reuploaded it to my datazap.
First I thought clutch slip, but nope your RPM to OSS indicate no problem with clutch or transmission.
I notice your load is slightly low from what I would expect. I suspect your fuel pump is maxed out.
The way I check this is I take your load as a fraction and through some math convert it to a rough MAF value. Then compare what your MAF sensor says and what the ECU is saying from load. Usually they are dead on, except in transients, unless you have a fuel issue that was compensated for.

From the picture you can see MAF from load is lower than than your MAF sensor. The ECU is compensating for a lack of fuel rail pressure relative to its inferred pressure tables, my guess. Then again its through out the entire range, so it could just be a vacuum leak.

Oh and why is this hurting performance? The car is thinking its moving more air than it really is, so everything is setup for that airflow instead of the actual airflow. Your KR slowly made its way to 8*, this is what the stock tune does. Get that down to 2-3* and having all the timing available right a way makes a big difference in the way the car feels.

Wow, I guess I'll check for a vacuum leak. Could my fuel pump be going bad? I've never heard of anyone needing a BAP for just bolt ons. Thanks! I guess I'm not crazy after all. Also you mention airflow, I'm not using the stock MAF sensor. I bought the PMAS No Tune required intake but never switched back to the stock MAF sensor once I got a tune. Could this be tune related for them not taking that into account? I told them I still was using the PMAS MAF sensor.

Also here's my log before the Longtubes. Are you seeing the same thing with this one as well?

https://datazap.me/u/brianh922/lund-e85r-18-mani-lu47s-stock-headers?log=0&data=1

aleccesarenriquez · Jun 23, 2018

Brianh922 said:
Wow, I guess I'll check for a vacuum leak. Could my fuel pump be going bad? I've never heard of anyone needing a BAP for just bolt ons. Thanks! I guess I'm not crazy after all. Also you mention airflow, I'm not using the stock MAF sensor. I bought the PMAS No Tune required intake but never switched back to the stock MAF sensor once I got a tune. Could this be tune related for them not taking that into account? I told them I still was using the PMAS MAF sensor.

Also here's my log before the Longtubes. Are you seeing the same thing with this one as well?

https://datazap.me/u/brianh922/lund-e85r-18-mani-lu47s-stock-headers?log=0&data=1

I wonder if I'm having the same issue then? Really wish I could view my logs

markmurfie · Jun 23, 2018

Brianh922 said:
Wow, I guess I'll check for a vacuum leak. Could my fuel pump be going bad? I've never heard of anyone needing a BAP for just bolt ons. Thanks! I guess I'm not crazy after all. Also you mention airflow, I'm not using the stock MAF sensor. I bought the PMAS No Tune required intake but never switched back to the stock MAF sensor once I got a tune. Could this be tune related for them not taking that into account? I told them I still was using the PMAS MAF sensor.

Also here's my log before the Longtubes. Are you seeing the same thing with this one as well?

https://datazap.me/u/brianh922/lund-e85r-18-mani-lu47s-stock-headers?log=0&data=1

Nope, Load coverts to MAF dead on. If your tuner knows its the Pmas no tune MAF in a Pmas housing, They should have it where it needs to be. What happens tho is if your fuel pressure is low, since its inferred, they can end up raising the MAF to compensate. Could just be an exhaust leak causing a false lean too, since it happened after exhaust work.

Brianh922 · Jun 23, 2018

Well my dyno confirmed it must be me. 453/393. Did 3 pulls, 2 with the hood closed and one with the hood open. Both of the hood closed pulls were consistent with 446/386. Mark I didn't make any changes to car other than double checking the vacuum routing and make sure there wasn't a leak. So is it just the way my tune is setup or is there something possibly wrong with my fuel system?

5ABI VT · Jun 24, 2018

3750 lbs car. installed higher rpm manifold and locks out the part that improves low speed torque. Adds long tube headers which can reduce low rpm torque for midrange and high rpm. wonders where torque went:headbonk: All kidding aside i think its the sotp meter thats fooling you. This is where theres value in phone apps or using the track app in the car to check the actual times. I also do pulls in gear before and after mods and can see the gains etc.

Brianh922 · Jun 24, 2018

5ABI VT said:
3750 lbs car. installed higher rpm manifold and locks out the part that improves low speed torque. Adds long tube headers which can reduce low rpm torque for midrange and high rpm. wonders where torque went:headbonk: All kidding aside i think its the sotp meter thats fooling you. This is where theres value in phone apps or using the track app in the car to check the actual times. I also do pulls in gear before and after mods and can see the gains etc.

I agree lol. Just glad I didn't have an issue at this point. Now on to get some track times and see what she's really gonna do.

Chach805 · Jun 24, 2018

I ran into the same issue when i put my headers on. I thought it felt so slow but It’s just the loss in torque your feeling from getting bigger headers plus not having catts.

5LITERV8 · Jun 24, 2018

Are these 1-7/8" or 1-3/4"? I wonder if that makes any difference.

66sprint6 · Jun 25, 2018

My "Butt Dyno" or SOTP meter as I saw it called earlier says the exact same thing with my GT. After the 18 manifold swap on stock exhaust manifolds I noticed the lower end torque drop but up top it would screeeeeeeeeeeeeeaaam. Added longtubes and the low end torque now feels better but it feels kinda off up top. Did some logging, all looks fine. Finally took it to the track and its running quicker MPH than before AND its on a Bias Ply now which often slows your MPH and Im running quicker ET's than ever before so my vote is also that it might be in your head. Especially after your dyno #'s.

Matt

Ronnoc · Jun 25, 2018

I didn't experience this in my FBO car tuned by lund. I also went with stepped headers which apparently help with low down tq. I did all my bolt ons at once but definitely no noticeable loss in tq.

Sluggish/Slower Coyote after Longtubes

Brianh922

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markmurfie

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Nuked

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Brianh922

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aleccesarenriquez

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markmurfie

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Brianh922

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5ABI VT

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Brianh922

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Chach805

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5LITERV8

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66sprint6

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Ronnoc

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