03 cobra dyno results!!!good or bad?

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grey03cobravert

New Member
Sep 20, 2006
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#1
i got a 03 cobra vert 27k miles, i got bassanai x pipe no cats,borla stinger exhast, stock manifolds still, accufab single blade with polished plemun,C/L inlet tube,a big air #2400 mass air,K/N FIPK filter,2.75 pulley and idler, 20 psi boost,steeda 03/04 sport springs,M/M full length frame connectors,tri axe shifter,and chip from JMS.hilton boost gauge overlay. JMS ported eaton,and a 6lb lower crank pulley. OK dyno #s are 490rwhp at 5000 rpms and 576 tq at 3500 rpms . run a 12.85 at 114 mph with goodyear F1's spinnig and wheel hopping 1st and 2nd gear. drag nitto's r's too come next one got 1 pass cause of my vert....is my hp low you think? tq looks good.
4DD45DC290AC494A80330BC42A038821.jpg
 

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#2
Your horsepower is low for that combo. The 2.75 coupled with a 6lb lower is really over-spinning the living crap out of the blower. Usually a ported Eaton loses most of it's efficiency somewhere around 16-17lbs of boost. Your combo (allowing for zero belt slip) is making somewhere around 18lbs of boost and spinning the blower in the neighborhood of 21500 RPMS! :eek:

I know Stiegemeier stage 4 port jobs are good for more than 500RWHP with less mods and less boost than you currently have... I'm not going to say the problem definitely lies with the JMS port... but if I had to blame a specific area that's what it would be. I also noticed your dyno chart is displaying STD numbers, what did it make SAE? What were the conditions?

U.M.
 
#3
Uncle Meat said:
Your horsepower is low for that combo. The 2.75 coupled with a 6lb lower is really over-spinning the living crap out of the blower. Usually a ported Eaton loses most of it's efficiency somewhere around 16-17lbs of boost. Your combo (allowing for zero belt slip) is making somewhere around 18lbs of boost and spinning the blower in the neighborhood of 21500 RPMS! :eek:

I know Stiegemeier stage 4 port jobs are good for more than 500RWHP with less mods and less boost than you currently have... I'm not going to say the problem definitely lies with the JMS port... but if I had to blame a specific area that's what it would be. I also noticed your dyno chart is displaying STD numbers, what did it make SAE? What were the conditions?

U.M.
Click to expand...
hey U.M iam nitrous408 btw m i lost my password when i got new puter.and i couldnt retrive my password with old mail box..i thought i ws gong to make about 520rwhp. i had 17 psi boost with the 3.0 upper dropped to 14 psi...with the 2.75 iam making 20psi dropping to 17 psi.the dyno shows the 2.75 pulley help. 60 more ft lbs of tq. while maken 576 tq at 3500. so that combe worked better. i think that is some high tq #s for a eaton right ? i dont think its the jms port. you think maybe i need long tube headders?dunno help me out . gary.you think headder would get me another 30hp? also is swapping the irs to live axle worth it ? the dyno temp was 91.65 deg hum was 14% b/ pressure was 29.91 they didnt have the rpm #s at the bottom of that print out , so at 60mph was 3000rpms, 80 / 4000, 100 / 5000, 120 /6000.
 
#4
Your torque looks good, but that's because of the insane pulley combo you're running. That combo really spins up the blower fast which results in those great TQ numbers down low. Long tube headers would definitely give you some extra ponies no doubt about it. Just keep in mind LT's are a pain to install on these cars.

Your low HP may have a lot to do with the high temps during the pull (91 degrees!). Additionally... your dyno sheet appears to be from a "Dynojet", yet JMS advertises they use a Mustang Dyno? So which is it? If the numbers you're reporting are from a Mustang dyno and NOT a dynojet then they are GREAT NUMBERS!

As for IRS vs solid axle... If you want to do some serious drag racing and want to get the best & most consistent launches then dump the IRS and put a solid in it. You also save almost 150lbs too!

U.M.
 
#9
careful...20 psi is blowing fire through the motor!!!

I made 490 with 15 psi. Your torque is so high because your eaton hasn't overspun yet....that is why your hp is low.......AND I just saw that UM put the same thing....oh well, it's early.
 
#10
Uncle Meat said:
Your torque looks good, but that's because of the insane pulley combo you're running. That combo really spins up the blower fast which results in those great TQ numbers down low. Long tube headers would definitely give you some extra ponies no doubt about it. Just keep in mind LT's are a pain to install on these cars.

Your low HP may have a lot to do with the high temps during the pull (91 degrees!). Additionally... your dyno sheet appears to be from a "Dynojet", yet JMS advertises they use a Mustang Dyno? So which is it? If the numbers you're reporting are from a Mustang dyno and NOT a dynojet then they are GREAT NUMBERS!

As for IRS vs solid axle... If you want to do some serious drag racing and want to get the best & most consistent launches then dump the IRS and put a solid in it. You also save almost 150lbs too!

U.M.
Click to expand...
im not sure what dyno it is , i will call them to see . i just tryed some 17x10.5 rims with bfgr kd's not dr's but didnt spin as much still had little wheel hop.
 
#11
its a dyno jet.. well with the 3.00 upper and the 9.0 lower i made 470rwhp and 511 rwtq. with 17psi boost it dropped of to 14psi i held the gauge,,, and with the 2.75 upper i swapped there during cool down it made 490rwhp and 576rwtq. had 20 psi boost then dropped to 17psi . so isnt that to say the 2.75 pulley made more hp and tq, so its better ? right? also my injectors are not pegged yet, no bap.
 
#12
SVT98Snake said:
careful...20 psi is blowing fire through the motor!!!

I made 490 with 15 psi. Your torque is so high because your eaton hasn't overspun yet....that is why your hp is low.......AND I just saw that UM put the same thing....oh well, it's early.
Click to expand...
isnt tq is what you want for a street car ?. i short shift about 5500 so the tq stays high also where the hp and tq drops off at ..is the right or should i be shifting higher like 6000 or 6500?
 
#14
iknow meat but they want 1000 bucks for a complete one. it just has stock internals 28 splines out of a 03 mach1 ? you think i need one? is that i good price for a complete one 1000 bucks? shock springs and all c/ arms abs sensors??? will the 28 splines hold up to my car , the mach1 had 3.555 just like my cobra got .?
 
#16
Uncle Meat said:
You should be able to find a GT owner who will trade you their stock 8.8 + cash for your IRS. Just post a "Want To Trade" message in the regional classifieds.

U.M.
Click to expand...
i can get a gt one for 700 bucks , but the mach1 has larger 13 in rotors in the back and i wont have to swap the gears either. is worth the extra 300. heck i'll sell my irs for 1200 bucks that will pay for shipping cost no the mach1 rear. i just need to change the drive shaft flange on the rear if iam correct? and use same drive shaft too?
 
#17
grey03cobravert said:
i got a 03 cobra vert 27k miles, i got bassanai x pipe no cats,borla stinger exhast, stock manifolds still, accufab single blade with polished plemun,C/L inlet tube,a big air #2400 mass air,K/N FIPK filter,2.75 pulley and idler, 20 psi boost,steeda 03/04 sport springs,M/M full length frame connectors,tri axe shifter,and chip from JMS.hilton boost gauge overlay. JMS ported eaton,and a 6lb lower crank pulley. OK dyno #s are 490rwhp at 5000 rpms and 576 tq at 3500 rpms . run a 12.85 at 114 mph with goodyear F1's spinnig and wheel hopping 1st and 2nd gear. drag nitto's r's too come next one got 1 pass cause of my vert....is my hp low you think? tq looks good.
4DD45DC290AC494A80330BC42A038821.jpg
Click to expand...

Boost looks to be too high, also I can't read A/F well due to the size of scale on the graph, but looks like it is over the ideal of around mid to high 11's. I'd think that you would do better with stock or 2# lower.
 
#18
It looks like you're just spinning the blower to fast. Low end is great, but you got nothin up top. I'd put a 2lb lower on there or a stock uppper.. You're HP will go down, but you'll be running the blower much more effieiently. With the stock upper, you'll have no problem with belt slip either..
 
#19
grey03cobravert said:
isnt tq is what you want for a street car ?. i short shift about 5500 so the tq stays high also where the hp and tq drops off at ..is the right or should i be shifting higher like 6000 or 6500?
Click to expand...

yeah, but you asked about numbers....tq is good hp is low. All I did was explain why :D

Don't shift past 6K with that much rpm...the higher you spin, the more heat you put through the motor. You will melt pistons if you aren't careful.
 
#20
UPDATE !!! well my rpmoutlet lower 6lb pulley is eating belts up. motoblue crap is cheap. iam trying to get credited, one day ...WELL HERES WHAT IAM THINKING OF DOING NOW ,,ok either kenne bell or whipple. 60 lb injecters , B.A.P another dyno tune , i put my stock lower back on now. belts not walking anymore , no more belt issues, anfter slinging 4 belt and tearing up a hood pad , i took that rpmout crap off. DONT BUY FROM THEM ...unless you want to go crazy...what you think of the new blower? i want at least 18 psi boost with pump gas. what size upper i need the 7.5 stock lower? to make that ,, ps do they make a 2.4 anymore ,, or do it change to the 2.6l?
 
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