Low dyno numbers
07-14-2013, 09:57 PM
#1
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Join Date: Apr 2010
Location: Upstate NY
Posts: 76
Low dyno numbers
Did the typical top end on my 1997 SS M6 w/ 88K and dropped it off for a tune last week. Drove the car for about 150 miles which included the trip to the tuner. Car seemed to drive well and was sporting the default 28lbs injectors and stock throttle body. The tuner ordered a set of 42LB green tops and installed and tuned. They were going to do some baseline pulls and then switch to a 52 or 58 throttle body to see what the difference was and go from there.
Stopped down Friday and numbers were way off.. This is a very reputable experienced shop who has delt w/ the LT1’s/LS’s forever. I have read lots of people say its just a number etc… I see the results they get from similar cars and lots of newer cars w/ different add ons.. The numbers always look as they should relating to the mods on the particular setup.. They use a Dynomite Dynamometer 1300 and I see the numbers for similar cars and newer ones. The numbers Friday were 330hp and I think 347 trq with AFR in mid 12’s.. I think he said when leaning did nothing and adding fuel decreased HP. Peaked power @ 5500..
Below is the setup.
LE2 Heads w/
205 cc intake port
Manley 2.00/1.56 6000 series valves
Patriot Gold Extreme springs (155 lbs seat and 400 lbs open)
victor reinz head gasket
ported intake
Custom Comp Cam 223/231 571/556 LSA 112
Comp Ultra Pro Rockers 3/8 1.6
Comp Push Rods part#7938-16 5/16 7.100
Plugs - NGK TR6 plugs gapped @ .050
Fuel Pump - Racetronix fuel pump
Thermostat - 160 degree
Exhaust - Pacesetter long tubes and high flow cats
Ignition - Stock Optispark and Coil
LE2 Ported Heads & Ported Intake with 58MM Throttle Body Holes
Pacesetter long tubes
2 high flow cats
new NTK O2's
new taylor 8.5's
for now stock TB
stock 3.42
315/35/17 nitto rears
T56 Center
centerforce stage 3
tuned out airpump
Just got an email from the shop tonight:
Swapped plugs to NGk 55 “pretty sure gapped to .035” what they recommended when I dropped it off.
Verified the injector connectors where correct.
Compression check on cylinders all within 2% 175-180
Checked ignition wires, Optispark high and low pulses, fuel pressure and regulator, cleaned MAF..
The said it was still down 50-70hp.. didn’t say what I pulled today but sound like it did on Friday..
What could it be?
Stopped down Friday and numbers were way off.. This is a very reputable experienced shop who has delt w/ the LT1’s/LS’s forever. I have read lots of people say its just a number etc… I see the results they get from similar cars and lots of newer cars w/ different add ons.. The numbers always look as they should relating to the mods on the particular setup.. They use a Dynomite Dynamometer 1300 and I see the numbers for similar cars and newer ones. The numbers Friday were 330hp and I think 347 trq with AFR in mid 12’s.. I think he said when leaning did nothing and adding fuel decreased HP. Peaked power @ 5500..
Below is the setup.
LE2 Heads w/
205 cc intake port
Manley 2.00/1.56 6000 series valves
Patriot Gold Extreme springs (155 lbs seat and 400 lbs open)
victor reinz head gasket
ported intake
Custom Comp Cam 223/231 571/556 LSA 112
Comp Ultra Pro Rockers 3/8 1.6
Comp Push Rods part#7938-16 5/16 7.100
Plugs - NGK TR6 plugs gapped @ .050
Fuel Pump - Racetronix fuel pump
Thermostat - 160 degree
Exhaust - Pacesetter long tubes and high flow cats
Ignition - Stock Optispark and Coil
LE2 Ported Heads & Ported Intake with 58MM Throttle Body Holes
Pacesetter long tubes
2 high flow cats
new NTK O2's
new taylor 8.5's
for now stock TB
stock 3.42
315/35/17 nitto rears
T56 Center
centerforce stage 3
tuned out airpump
Just got an email from the shop tonight:
Swapped plugs to NGk 55 “pretty sure gapped to .035” what they recommended when I dropped it off.
Verified the injector connectors where correct.
Compression check on cylinders all within 2% 175-180
Checked ignition wires, Optispark high and low pulses, fuel pressure and regulator, cleaned MAF..
The said it was still down 50-70hp.. didn’t say what I pulled today but sound like it did on Friday..
What could it be?
07-14-2013, 11:28 PM
#2
Super Moderator
Join Date: Jul 2005
Location: Okemos, MI
Posts: 9,485
Re: Low dyno numbers
Seems like it should be peaking at a higher RPM with that head/cam combo. Are they running it to 6500? I'd like to see what it's doing power-wise from 5500 up. Normal culprits for high-RPM power issues are valve float, spark, and fuel. Given that you have a fully upgraded valve train and fuel system and the Opti tests good, I'd be looking very closely at that stock coil.
07-14-2013, 11:40 PM
#3
Registered User
Thread Starter
Join Date: Apr 2010
Location: Upstate NY
Posts: 76
Re: Low dyno numbers
I suggested the coil tonight.. I was also thinking about the 02 sensors.. I forgot to order 02 extensions and we ended up extending the wire on the 02 sensors.. Could they be reporting not accurate info throwing things way off? I asked that the rears be tuned out and the front two are BN.. I read tonight extending the o2 is not recommend and it got me thinking.. just stabbing in the dark
07-15-2013, 08:35 AM
#9
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Thread Starter
Join Date: Apr 2010
Location: Upstate NY
Posts: 76
Re: Low dyno numbers
Yes that was right off the Cam Card from Comp.. With 1.6 Rockers the end result .610/.594..
The HP/TRQ curves were increasing smoothly didnt look like a EKG or anything.. I will try and get a screenshot or photo of the dyno pull..
The HP/TRQ curves were increasing smoothly didnt look like a EKG or anything.. I will try and get a screenshot or photo of the dyno pull..
07-15-2013, 10:13 AM
#10
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Join Date: Jun 2000
Location: Washington, Michigan USA
Posts: 857
Re: Low dyno numbers
If your dyno curve looks smooth with NO evidence of either valve float or ignition breakup then your problem lies here:
"Pacesetter long tubes and high flow cats".
Your once "high flowing" cats are not high flowing with your new top end set up. The reason your engine is "nosing over" at 5,500 RPM is most likely now due to backpressure on your exhaust side.
Everyone's exhaust set up is different, but, can you easily drop your y-pipe and cats and do a pull through just your LT Pacesetter headers???
One (1) test is worth one thousand (1,000) opinions.
"Pacesetter long tubes and high flow cats".
Your once "high flowing" cats are not high flowing with your new top end set up. The reason your engine is "nosing over" at 5,500 RPM is most likely now due to backpressure on your exhaust side.
Everyone's exhaust set up is different, but, can you easily drop your y-pipe and cats and do a pull through just your LT Pacesetter headers???
One (1) test is worth one thousand (1,000) opinions.
Last edited by 97 6SPEED Z; 07-15-2013 at 10:17 AM.
07-15-2013, 10:46 AM
#11
Registered User
Thread Starter
Join Date: Apr 2010
Location: Upstate NY
Posts: 76
Re: Low dyno numbers
The exhaust is band clamped together so a pull w/ open headers is an option.. I am just waiting on a call or may stop down again today and will throw that out there if they are still coming up way short.. Thanks for your inputs..
07-15-2013, 11:31 AM
#12
Registered User
Join Date: Apr 2006
Location: New York
Posts: 512
Re: Low dyno numbers
Hey sean its justin from cdcny-- i had the same issue w mine.. low numbers... my car got tuned speed density and it brought me another 43/39 or something llikethat.. i layed down 310/330 then after speed density tune i ended up w 353/369-- i know those guys over there know what their doing but i know the "other" tuning shop in are area did it that way w me. LOL good luck man!!!
