Disappointing dyno numbers...were my expectations too high?
10-02-2015, 10:22 PM
#1
Teching In
Thread Starter
Disappointing dyno numbers...were my expectations too high? Well, i finally got around to getting the car dynoed with the new engine. The build is in my signature. The shop is a fairly reputable shop in the area and is full of high end LS cars (CTVs, new ZO6s, Corvettes everywhere). Their dyno is know to be a little stingy but i gotta say i was pretty shocked with the numbers.
A little background first. The previous tune was for the stock LS2 and same blower. Stock exhaust, stock everything except the fuel system and blower and made 493hp/515lbft. This was roughly confirmed, based on weight/hp calculators, with trap speeds anywhere from 118-119.5 with horrible 60ft times. Apparently, this tune was straight garbage with improper VE tables and horrible transition between the midrange tables and WOT. The car drove like a dream but i will admit the mpgs were pretty horrible just cruising around in the city.
Now, as you can see in my sig, i DO have a smaller displacement motor, but everything else has been built to support higher rpm and better flow. The car ran fairly well with the old tune and new engine but it was super rich and had its hiccups, mainly with horrible mpgs and a miss under acceleration while in cruising gears (this ended up being because i burned up the cats do to the rich tune). Power delivery was good, however, and seemed to be just as strong as the old combo.
The tuner advised me to go to an SD tune, so i said sure, why not. The car isnt a track car but ive read about how boosted cars respond better to an SD tune so i said go for it. When i went to get the car today he said he didnt do a full SD tune...He said since its a street car the MAF is really the best thing for the car so he did a partial SD tune that still utilizes the MAF. Id never heard of such a thing but since im not an experienced tuner i said ok.
He was very knowledgeable and explained in detail all the changes he made and showed me the numerous runs he made from baseline to end state. He said he enriched the WOT AFRs from low-mids 12s down to high 11s for safety and that seemed reasonable.
Well, after all the suspense, i finally asked for the numbers...and man was i shocked when he puled it up on the screen. 403hp/400lbft at 8psi. Yikes. Even with the stingiest dyno and horrible conditions I was expecting at least mid to high 400s. Once i get the graphs ill post them but something else that struck me as odd was the power drop off at higher rpms. It seemed to pull to 5800rpms and gradually drop off after that. That's what i would expect with a stock cam but i fully expected this thing to keep making power well into the 6000s. In the end, i knew dyno numbers only mean so much so i got my keys, paid the bill and made my way back to work.
Initial driving impressions left me even more disappointed. It DID idle better and i could tell it was leaner just by the crackle of the exhaust. The car has a very noticeable lean stumble anytime i press the accelerator down in any way but gradually and watching my wide band confirms this as it jumps to 18 before fuel enrichment kicks in. This happens in all gears and at any speed. The real kicker is, it feels slower. It's the weirdest feeling but at WOT the power feels "smoother" but it doesn't seem to pull as hard.
In the end i called him back and told him all this and he seems willing to do whatever it takes to make me happy so that's good. For now if i can get the stumble tuned out and maybe lean the WOT back to where it was I'll be happy until i can figure out the power drop off at high rpm. Also, i think i might move to an LS3 MAF and get rid of the SD part of the tune.
Any input would be appreciated.
A little background first. The previous tune was for the stock LS2 and same blower. Stock exhaust, stock everything except the fuel system and blower and made 493hp/515lbft. This was roughly confirmed, based on weight/hp calculators, with trap speeds anywhere from 118-119.5 with horrible 60ft times. Apparently, this tune was straight garbage with improper VE tables and horrible transition between the midrange tables and WOT. The car drove like a dream but i will admit the mpgs were pretty horrible just cruising around in the city.
Now, as you can see in my sig, i DO have a smaller displacement motor, but everything else has been built to support higher rpm and better flow. The car ran fairly well with the old tune and new engine but it was super rich and had its hiccups, mainly with horrible mpgs and a miss under acceleration while in cruising gears (this ended up being because i burned up the cats do to the rich tune). Power delivery was good, however, and seemed to be just as strong as the old combo.
The tuner advised me to go to an SD tune, so i said sure, why not. The car isnt a track car but ive read about how boosted cars respond better to an SD tune so i said go for it. When i went to get the car today he said he didnt do a full SD tune...He said since its a street car the MAF is really the best thing for the car so he did a partial SD tune that still utilizes the MAF. Id never heard of such a thing but since im not an experienced tuner i said ok.
He was very knowledgeable and explained in detail all the changes he made and showed me the numerous runs he made from baseline to end state. He said he enriched the WOT AFRs from low-mids 12s down to high 11s for safety and that seemed reasonable.
Well, after all the suspense, i finally asked for the numbers...and man was i shocked when he puled it up on the screen. 403hp/400lbft at 8psi. Yikes. Even with the stingiest dyno and horrible conditions I was expecting at least mid to high 400s. Once i get the graphs ill post them but something else that struck me as odd was the power drop off at higher rpms. It seemed to pull to 5800rpms and gradually drop off after that. That's what i would expect with a stock cam but i fully expected this thing to keep making power well into the 6000s. In the end, i knew dyno numbers only mean so much so i got my keys, paid the bill and made my way back to work.
Initial driving impressions left me even more disappointed. It DID idle better and i could tell it was leaner just by the crackle of the exhaust. The car has a very noticeable lean stumble anytime i press the accelerator down in any way but gradually and watching my wide band confirms this as it jumps to 18 before fuel enrichment kicks in. This happens in all gears and at any speed. The real kicker is, it feels slower. It's the weirdest feeling but at WOT the power feels "smoother" but it doesn't seem to pull as hard.
In the end i called him back and told him all this and he seems willing to do whatever it takes to make me happy so that's good. For now if i can get the stumble tuned out and maybe lean the WOT back to where it was I'll be happy until i can figure out the power drop off at high rpm. Also, i think i might move to an LS3 MAF and get rid of the SD part of the tune.
Any input would be appreciated.
10-03-2015, 10:52 AM
#5
I'll throw my $0.02 in here because I've had similar experience.
All above suggestions & directions are correct.
First lets remember that we are speaking about two different motors, Dyno's , tunes etc. etc...
So what we are speaking of is a 5.3 ( mods in sig) w/ Maggie on top.
No doubt your numbers are low.
1. I have no doubt you have belt slip. That may not make up for the deficit, but you have it. ( unless you have upgraded to an 8 rib system). Many will tell their tales of no slip etc... But trust me .... You are slipping and it will cost a few ponies on top & bottom. Are you holding 8 lbs straight through to 6k. The chosen cam is known for low overlap and ( even with those heads) you should hold about 9-10 on the 5.3 motor.
2. The compression makes a diff., these Maggie's need all the help we can get. I had to go to 11.2:1 to squeeze out a few more ponies and get the sharp/peppy response that I wanted.
3. Clutch slip: I dealt with this every time I added a new substantial mod to the car. Didn't learn my lesson until I was tired of spending money & wasting time. In my opinion there is no such thing as overkill when it comes to a clutch. With that said, IF your motor IS in fact putting out the proper numbers ( which won't be more much than 500/500) the stage two is on the borderline of holding up. The TQ will slip it for sure as these Maggie's can hit the 400 lbs practically off idle. Rise up to 500 @ about 5200rpm. I smoked a brand new ( well broken in LS7 clutch) on the Dyno and it drove us nuts on the first few pulls. ( same as you).
4. Dyno: is it a Mustang or Dyno jet. ( as compared to your previous sheet). I know we are splitting hairs .... But all of these hairs add up to a big wig !!!
20 hp here 15hp there and the Dyno can be about 8% or so off.
Show Slowhawk your sheet. He knows his stuff & will point you in the right direction.
All above suggestions & directions are correct.
First lets remember that we are speaking about two different motors, Dyno's , tunes etc. etc...
So what we are speaking of is a 5.3 ( mods in sig) w/ Maggie on top.
No doubt your numbers are low.
1. I have no doubt you have belt slip. That may not make up for the deficit, but you have it. ( unless you have upgraded to an 8 rib system). Many will tell their tales of no slip etc... But trust me .... You are slipping and it will cost a few ponies on top & bottom. Are you holding 8 lbs straight through to 6k. The chosen cam is known for low overlap and ( even with those heads) you should hold about 9-10 on the 5.3 motor.
2. The compression makes a diff., these Maggie's need all the help we can get. I had to go to 11.2:1 to squeeze out a few more ponies and get the sharp/peppy response that I wanted.
3. Clutch slip: I dealt with this every time I added a new substantial mod to the car. Didn't learn my lesson until I was tired of spending money & wasting time. In my opinion there is no such thing as overkill when it comes to a clutch. With that said, IF your motor IS in fact putting out the proper numbers ( which won't be more much than 500/500) the stage two is on the borderline of holding up. The TQ will slip it for sure as these Maggie's can hit the 400 lbs practically off idle. Rise up to 500 @ about 5200rpm. I smoked a brand new ( well broken in LS7 clutch) on the Dyno and it drove us nuts on the first few pulls. ( same as you).
4. Dyno: is it a Mustang or Dyno jet. ( as compared to your previous sheet). I know we are splitting hairs .... But all of these hairs add up to a big wig !!!
20 hp here 15hp there and the Dyno can be about 8% or so off.
Show Slowhawk your sheet. He knows his stuff & will point you in the right direction.
10-03-2015, 12:32 PM
#6
I should add two more possibilities to the mix.
1. Heat soak: I experienced a 50hp variance compared to a heat soaked motor & not.
The IATs on a Maggie are nuts. If the Dyno was done on the first run under cooler conditions or was this done after multiple tuning runs ? Needless to say that explains itself.
On the new tune compared to the old what are the IAT timing tables. Most Maggie guys pull timing @ 140*. Without a proper intercooler / heat exchanger you can hit that number real quick. That brings us to the next possibility.
2. Timing: I'm not trying to point fingers at the tune but if you can get as much logged info from the tuner, someone on these boards ( much more experienced than I) can help decipher. I know most Maggie tunes run timing a lot higher than most FI posts I see. We were running 19* without the meth. No signs of detination etc. I'm not suggesting that. Just suggesting that a very conservative tune makes a big difference as well. As a matter of fact I commend the tuner for suggesting 11's as apposed to high 12's on the AFR. It brought back memories for me as I had the same experience when I was also disappointed in my first run with the new Maggie. I saw some peak numbers that I liked ( I no longer obsess over peak numbers ... It's just a number) and the tuner quickly said, well that's at 12.2 AFR. .... Not going to stay there. We brought it down to mid 11' s and the sheet certainly reflected it. At the end of the day you don't want to put your motor at risk just because you want to chase a ghost.
Same goes for timing.
So. Add IATs & timing to the list things to explore.
Hang in there, you have all the components for a fun ride. I realize you are only trying to bring this build up to parr however, My predominant suggestion would be to not chase unsafe tuning for the sake of bragging rights.
1. Heat soak: I experienced a 50hp variance compared to a heat soaked motor & not.
The IATs on a Maggie are nuts. If the Dyno was done on the first run under cooler conditions or was this done after multiple tuning runs ? Needless to say that explains itself.
On the new tune compared to the old what are the IAT timing tables. Most Maggie guys pull timing @ 140*. Without a proper intercooler / heat exchanger you can hit that number real quick. That brings us to the next possibility.
2. Timing: I'm not trying to point fingers at the tune but if you can get as much logged info from the tuner, someone on these boards ( much more experienced than I) can help decipher. I know most Maggie tunes run timing a lot higher than most FI posts I see. We were running 19* without the meth. No signs of detination etc. I'm not suggesting that. Just suggesting that a very conservative tune makes a big difference as well. As a matter of fact I commend the tuner for suggesting 11's as apposed to high 12's on the AFR. It brought back memories for me as I had the same experience when I was also disappointed in my first run with the new Maggie. I saw some peak numbers that I liked ( I no longer obsess over peak numbers ... It's just a number) and the tuner quickly said, well that's at 12.2 AFR. .... Not going to stay there. We brought it down to mid 11' s and the sheet certainly reflected it. At the end of the day you don't want to put your motor at risk just because you want to chase a ghost.
Same goes for timing.
So. Add IATs & timing to the list things to explore.
Hang in there, you have all the components for a fun ride. I realize you are only trying to bring this build up to parr however, My predominant suggestion would be to not chase unsafe tuning for the sake of bragging rights.
10-03-2015, 01:27 PM
#7
Teching In
Thread Starter
Thanks for all the input. Definitely, gives me lots to think about. I'm still waiting for them to send me the graphs but i do know the compression is 10.25:1. I'll keep an eye on the clutch and belt. I used to be able to tell when my old belt would slip because it would leave belt dust all over and this one has yet to do that.
I agree with you on chasing numbers and that's certainly not what i care most about. We'll start with the easy stuff and work through the rest until things come together.
I agree with you on chasing numbers and that's certainly not what i care most about. We'll start with the easy stuff and work through the rest until things come together.
