30 wheel horsepower loss? - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

Jakey2SS · 09-11-2014, 07:20 PM

I will make a long story as short as I can.. only mods are CAI and straight pipes, L99 car..had it custom tuned last month, car made 357whp after the tune, made 327 whp before the tune). Took vehicle back today to have the throttle body ported and have another few dyno pulls to compare. The shop calls me up boasting that the car now makes 341whp up from 327whp from before the throttle body porting. My response was naturally... why is it now making 327whp but made 357whp a few weeks ago when I had it tuned? His initial response was that they dyno'd it when it was warmer outside today than the previous time, and that's why it made 30whp less. (The guy who actually tuned the car is currently on medical leave for 2 weeks by the way)

I go to pick up the car and I question the guy who does some minor tuning who works there, and who actually ported the throttle body. He blames it either on the gas, or on the car, the car has 14k miles. He blames it on possible poor fuel pressure, possible bad spark plug, possible bad this, that and the other thing. I would like some opinions on this from you guys.. the car still pulls hard but I have noticed it being a tad more sluggish the last week. I always gas up at the same station with 91, vehicle idles smooth and drives the same. I have already contacted another shop here in town that immediately tells me has re-tuned numerous cars that this other guy has touched. Anything I can check in the mean time? (cant take the car into the other shop until sometime next week) I work as a service advisor at a dealership so getting anything tested/looked at is not a problem.

jergarr · 09-11-2014, 08:23 PM

Weak MAF sensor?

raptor5244 · 09-11-2014, 08:46 PM

Do you mean 357hp vs 341hp? If so, was it indeed much hotter and more humid between dyno runs? It will make a difference. Down here in Florida I can tell right away once we get our first cold front after a long hot and humid summer.

The throttle body porting won't really add more horsepower but it should improve throttle response. As for the tune, the improvement in power has to due with increasing the timing for your fuel octane level and modifying the power enrichment table to lean it out a little bit for wide open throttle. If done correctly, you gain about 10hp or so from the just tune. I see you run 91 octane so that will limit the amount you can bump your timing.

When you say straight pipe, are you referring to a cat back, no mufflers? If so, there is not much power gain there either. You need long tube headers with high flow cats on these engines to yield any significant gains from exhaust mods.

Scott@Bjorn3D · 09-11-2014, 08:46 PM

Could be bad fuel. If they did not the tune of the high octane table to the low one it could of went to low octane mode. That will cut 50-60 back wheel HP and 40-50 pounds of torque to the back wheels. Go get gas at a different station and run a tank or two thru it. The pull fuse 5 and 20 in the engine bay for at least 3 hours and let us know the outcome.

Jakey2SS · 09-11-2014, 09:10 PM

Quote:

Originally Posted by raptor5244

Do you mean 357hp vs 341hp? If so, was it indeed much hotter and more humid between dyno runs? It will make a difference. Down here in Florida I can tell right away once we get our first cold front after a long hot and humid summer..

It put down 327whp with just a CAI, 357whp with CAi and tune. Today (3 weeks after the tune) it put down 327whp again (30whp loss over previous dyno) and 341whp after the TB porting. 90 degrees outside.

Quote:

Originally Posted by Scott@Bjorn3D

Could be bad fuel. If they did not the tune of the high octane table to the low one it could of went to low octane mode. That will cut 50-60 back wheel HP and 40-50 pounds of torque to the back wheels. Go get gas at a different station and run a tank or two thru it. The pull fuse 5 and 20 in the engine bay for at least 3 hours and let us know the outcome.

I have read all about the fuse pulling but he told me he eliminated the 87 octane table. And by eliminated I don't know if you can literally get rid of it or it just stops the car from ever going into it, I am not THAT into tuning, but I do understand it.

raptor5244 · 09-11-2014, 10:00 PM

Quote:

Originally Posted by Jakey2SS

It put down 327whp with just a CAI, 357whp with CAi and tune. Today (3 weeks after the tune) it put down 327whp again (30whp loss over previous dyno) and 341whp after the TB porting. 90 degrees outside.

I have read all about the fuse pulling but he told me he eliminated the 87 octane table. And by eliminated I don't know if you can literally get rid of it or it just stops the car from ever going into it, I am not THAT into tuning, but I do understand it.

30 rwhp is too much for just a tune. They don't leave that much on the table. Realistically, you will get 10rwhp maybe 15rwhp with an aggressive tune on 93 octane. Cai is good for 10rwhp or so depending on the brand. Your numbers seem about right for a cai and tune on 91 octane. Just dyno it again in a couple months when it is cool and you will see it pick up some power.

As for the octane table, what you do is copy the timing values from the high octane table to the low octane table so that even if the ECU switches to the low table it will reflect the higher octane timing values. This may sound good but it can be bad. Say you or the next owner accidentally puts 87 octane or just gets a bad tank of gas. Well, the ECU uses it's knock sensors to determine if it should switch to the low octane table and pull timing but now your low octane table timing values aren't any lower so you just keep knocking. Not good. The low octane table is there to protect the engine in this scenario. If the low octane table was indeed modified then the fuse pull will have no effect since the values in both tables are the same.

Destructo09 · 09-11-2014, 10:54 PM

Is this shop using SAE corrected number or uncorrected or STD correction, etc?

If they're using uncorrected numbers then it's going to vary a good bit because of the weather. Ideally they should use SAE which should be pretty close and compensate for weather pretty well.

I think this question should be answered before any others.

Destructo09 · 09-11-2014, 10:56 PM

Quote:

Originally Posted by raptor5244

30 rwhp is too much for just a tune. They don't leave that much on the table. Realistically, you will get 10rwhp maybe 15rwhp with an aggressive tune on 93 octane. Cai is good for 10rwhp or so depending on the brand. Your numbers seem about right for a cai and tune on 91 octane. Just dyno it again in a couple months when it is cool and you will see it pick up some power.

As for the octane table, what you do is copy the timing values from the high octane table to the low octane table so that even if the ECU switches to the low table it will reflect the higher octane timing values. This may sound good but it can be bad. Say you or the next owner accidentally puts 87 octane or just gets a bad tank of gas. Well, the ECU uses it's knock sensors to determine if it should switch to the low octane table and pull timing but now your low octane table timing values aren't any lower so you just keep knocking. Not good. The low octane table is there to protect the engine in this scenario. If the low octane table was indeed modified then the fuse pull will have no effect since the values in both tables are the same.

I gained nearly 30 RWHP from a tune after putting my long tubes on.

Base dyno was 391, after they tuned it up I was at 421.

two_wheel_mayhem · 09-12-2014, 12:31 AM

Take it back when the real tuner returns from medical leave and give them a chance to make it right.

two_wheel_mayhem · 09-12-2014, 12:35 AM

Quote:

Originally Posted by Destructo09

Is this shop using SAE corrected number or uncorrected or STD correction, etc?

If they're using uncorrected numbers then it's going to vary a good bit because of the weather. Ideally they should use SAE which should be pretty close and compensate for weather pretty well.

I think this question should be answered before any others.

SAE is also corrected for altitude so it's a better number to use if comparing numbers with people from varying regions.

ytown87 · 09-12-2014, 07:38 AM

Are you putting the car on the track to see how this difference in dyno number is affecting the car or your times? If not, its irrelevant. The car obviously didnt feel any different to you in regular driving so... Cars can dyno different numbers every time you strap them down if the conditions arent exactly the same as the last.

Went to a dyno day here in FL where almost everyone that had been on that dyno at some earlier time before was dyno'd 20-30hp less than they had put down before. Yet none of them complained about 1/4 times suffering.

CamaroCracka · 09-12-2014, 02:09 PM

Quote:

Originally Posted by Jakey2SS

It put down 327whp with just a CAI, 357whp with CAi and tune. Today (3 weeks after the tune) it put down 327whp again (30whp loss over previous dyno) and 341whp after the TB porting. 90 degrees outside.

Were you there either time they ran it on the dyno? Seems a little suspicious (my wife does say I'm paranoid) that the starting number is 327 both times. Is it possible they did not realize you had paid them for a tune already and have not been putting your car on the dyno at all (to save them time) but just telling you numbers the sound good. Lots of unscrupulous shops out there. That is why I rarely let anybody work on my stuff and when I do, I let them know I am an azz about shoddy work before they start.

raptor5244 · 09-12-2014, 07:03 PM

Quote:

Originally Posted by Destructo09

I gained nearly 30 RWHP from a tune after putting my long tubes on.

Base dyno was 391, after they tuned it up I was at 421.

Sounds good. But it was the headers that provided the bulk of the power increase not the tune. Tunes are good for about 10-15rwhp. The purpose of the tune is get your fueling back inline after altering the airflow characteristics caused by the new air intake and exhaust. The power gain with a tune comes from optimizing the timing and leaning out the power enrichment table, which determines your AFR during WOT. When in the hands of an experienced tuner on the dyno they can find the sweet spot for you particular engine and the mods you have. A responsible tuner will create a safe tune and back off some of the timing to protect you from excess knock retard from a bad tank of gas.

The other benefits come from changing the fan settings, reducing or eliminated torque management during the transmission tune on an auto, disabling CAGS, etc. don't let anyone fool you into 30rwhp from the tune alone. The increase seen on the dyno sheet could be a result of cooler day, less humidity, less heat soaked engine, different dyno, etc.

09-11-2014, 07:20 PM	#1
Jakey2SS Drives: 15' Scat Pack Join Date: May 2014 Location: Fresno, Ca Posts: 281	30 wheel horsepower loss? I will make a long story as short as I can.. only mods are CAI and straight pipes, L99 car..had it custom tuned last month, car made 357whp after the tune, made 327 whp before the tune). Took vehicle back today to have the throttle body ported and have another few dyno pulls to compare. The shop calls me up boasting that the car now makes 341whp up from 327whp from before the throttle body porting. My response was naturally... why is it now making 327whp but made 357whp a few weeks ago when I had it tuned? His initial response was that they dyno'd it when it was warmer outside today than the previous time, and that's why it made 30whp less. (The guy who actually tuned the car is currently on medical leave for 2 weeks by the way) I go to pick up the car and I question the guy who does some minor tuning who works there, and who actually ported the throttle body. He blames it either on the gas, or on the car, the car has 14k miles. He blames it on possible poor fuel pressure, possible bad spark plug, possible bad this, that and the other thing. I would like some opinions on this from you guys.. the car still pulls hard but I have noticed it being a tad more sluggish the last week. I always gas up at the same station with 91, vehicle idles smooth and drives the same. I have already contacted another shop here in town that immediately tells me has re-tuned numerous cars that this other guy has touched. Anything I can check in the mean time? (cant take the car into the other shop until sometime next week) I work as a service advisor at a dealership so getting anything tested/looked at is not a problem.

09-11-2014, 08:23 PM	#2
jergarr Drives: 11' RJT 2SS/RS L99 Join Date: Jun 2014 Location: Chicago Posts: 298	Weak MAF sensor? __________________ GPI VVT3 Cam Circle D 3800 Single Disc Stall 1LE 3.91s Stainless Power Headers w/cats Fluidampr 25% UDP Cold Air Inductions Intake Bo White Ported Throttle Body ADM Trans Cooler Some BMR Goodies

09-11-2014, 10:54 PM	#7
Destructo09 Drives: 2010 CGM Camaro 2SS/LS3 Join Date: Oct 2013 Location: Raleigh-Durham Posts: 1,409	Is this shop using SAE corrected number or uncorrected or STD correction, etc? If they're using uncorrected numbers then it's going to vary a good bit because of the weather. Ideally they should use SAE which should be pretty close and compensate for weather pretty well. I think this question should be answered before any others. __________________ 2010 2SS BMR 1" Springs Koni Orange struts/shocks 1LE rear sway bar SRP Racing Pedals Hurst Billet short shifter Square tire/wheel setup Elite Engineering Catch Can Stainless Power longtubes/highflow cats K&N Typhoon CAI RPM Motorsports of Garner, NC dyno tune (421 RWHP)

09-12-2014, 12:31 AM	#9
two_wheel_mayhem Would rather be riding Drives: No car no more Join Date: Jul 2009 Location: Indiana Posts: 2,750	Take it back when the real tuner returns from medical leave and give them a chance to make it right. __________________ No dog in this fight anymore. 5th Gen owner 2009-2016.

09-12-2014, 07:38 AM	#11
ytown87 Drives: C6 Corvette Join Date: Sep 2013 Location: Tampa, FL Posts: 1,264	Are you putting the car on the track to see how this difference in dyno number is affecting the car or your times? If not, its irrelevant. The car obviously didnt feel any different to you in regular driving so... Cars can dyno different numbers every time you strap them down if the conditions arent exactly the same as the last. Went to a dyno day here in FL where almost everyone that had been on that dyno at some earlier time before was dyno'd 20-30hp less than they had put down before. Yet none of them complained about 1/4 times suffering. __________________ 2008 C6 m6. Carbon creations front/rear carbon fiber wodebody fenders. Carbon fiber hood carbon fiber roof hoop carbon fiber zr1 extreme spoiler. NW 102mm tb. Ported intake manifold. Cometic .040 head gaskets. LG motorsports G6x3 cam. DSX flex fuel sensor. AEM methanol kit. Z06 brakes. Ebiach sway bars. ZR1 rep wheels and Nitto Invo tires. Monster stage 3 twin disc clutch. MGW short shifter. Corbeau race seats. Gforce race harnesses. SLP loudmouth 2 mufflers. Carbon fiber exhaust tips. RPM stage 4 transmission and Stage 3 rear diff. 3.73 gears. Vararam cai. Kooks 1 7/8 headers and x-pipe.

09-11-2014, 08:46 PM	#3
raptor5244 Drives: 2022 CT4-V Blackwing Join Date: Sep 2013 Location: Florida Posts: 2,723	Do you mean 357hp vs 341hp? If so, was it indeed much hotter and more humid between dyno runs? It will make a difference. Down here in Florida I can tell right away once we get our first cold front after a long hot and humid summer. The throttle body porting won't really add more horsepower but it should improve throttle response. As for the tune, the improvement in power has to due with increasing the timing for your fuel octane level and modifying the power enrichment table to lean it out a little bit for wide open throttle. If done correctly, you gain about 10hp or so from the just tune. I see you run 91 octane so that will limit the amount you can bump your timing. When you say straight pipe, are you referring to a cat back, no mufflers? If so, there is not much power gain there either. You need long tube headers with high flow cats on these engines to yield any significant gains from exhaust mods.

09-11-2014, 08:46 PM	#4
Scott@Bjorn3D Drives: Kami, 2013 2SS LS3 Luvin Join Date: Oct 2008 Location: Eufaula, Alabama Posts: 6,427	Could be bad fuel. If they did not the tune of the high octane table to the low one it could of went to low octane mode. That will cut 50-60 back wheel HP and 40-50 pounds of torque to the back wheels. Go get gas at a different station and run a tank or two thru it. The pull fuse 5 and 20 in the engine bay for at least 3 hours and let us know the outcome.