Horsepower seems to be down.
03-07-2018, 10:41 AM
#1
Staging Lane
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Horsepower seems to be down. I’ve got a 03 silverado with lq4 swap. It has prc 2.5 5.3 heads, comp cams 54-458-11 cam which is 227/235 .614/.621, Holley hi ram intake, ford racing 39lb injectors, long tube headers, built 4l60 with yank 3600 stall and 4.10 gear. Had it tuned and dynoed and put down 358 to the tire. Was hoping to see at least 400 or a little more. Trying to figure out why this combo is down on power. Tuner says fuel isn’t an issue. Have plenty of fuel feeding it.
03-07-2018, 11:27 AM
#4
Dont worry about the number. mustang dyno will say 350 dynojet will say 400.
Instead try driving it. Race other cars you know are fast or take it to the track and check mph.
If you think something is wrong with the engine couple tests you can do:
1. compression test
2. leak down test
3. pressure test
Then try reducing air path restrictions, new air filter or better air filter plumbing. Use shields to protect air path from hot engine bay components. reduce the temp of the engine bay by adding ducts or installing shields. Reduce vehicle weight anyway possible, take stuff out of the truck, vacuum it, clean it, clean the dark recesses.
Reduce rolling resistance, check for brake drag, truck is fairly new so no issues with wheel bearings etc.. but check the alignment. Use a low rolling resistance tire, find the best tire pressure to roll easy. I just fill them up little by little and try pushing the vehicle by hand in neutral until it rolls easy.
Alllll kinds of stuff you can do to improve on what you have. The next big jump would be a 100 shot so fix everything do all ur diagnostics then consider an extra 100 shot of N2O. Or boost.
Instead try driving it. Race other cars you know are fast or take it to the track and check mph.
If you think something is wrong with the engine couple tests you can do:
1. compression test
2. leak down test
3. pressure test
Then try reducing air path restrictions, new air filter or better air filter plumbing. Use shields to protect air path from hot engine bay components. reduce the temp of the engine bay by adding ducts or installing shields. Reduce vehicle weight anyway possible, take stuff out of the truck, vacuum it, clean it, clean the dark recesses.
Reduce rolling resistance, check for brake drag, truck is fairly new so no issues with wheel bearings etc.. but check the alignment. Use a low rolling resistance tire, find the best tire pressure to roll easy. I just fill them up little by little and try pushing the vehicle by hand in neutral until it rolls easy.
Alllll kinds of stuff you can do to improve on what you have. The next big jump would be a 100 shot so fix everything do all ur diagnostics then consider an extra 100 shot of N2O. Or boost.
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03-07-2018, 12:46 PM
#8
Even with readouts being different from dyno to dyno, those numbers seem out of tolerance on the low side. Maybe the dyno is the issue and not your vehicle? Does it drive like its down on power?
03-07-2018, 12:50 PM
#9
Staging Lane
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It pulls ok for what it is but feels down somewhat. Track times are 8.34 at 86 mph in 1/8 and 13.07 at 104 in 1/4. I felt this truck should’ve been at least a mid 12 on motor
03-07-2018, 12:57 PM
#10
Ya id say your dyno result is accurate based on your mph. I plugged your mph and approximate vehicle weight (4250) into an online HP calculator. It gave a result of 370.
Your combo Should be making more power than that. Something could be wrong.
Your combo Should be making more power than that. Something could be wrong.
03-07-2018, 01:04 PM
#12
Sorry man I have no idea. The responses above provided some great ideas of things to try. However I would certainly have expected 400 whp out of that combo, although I'm no expert.
03-07-2018, 01:16 PM
#13
Staging Lane
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That’s what i was thinking too. I thought for the combo would’ve made 500+ at the flywheel but it just isn’t showing. I’ll start digging thru it more and see what i can find.
03-07-2018, 01:51 PM
#14
post a dyno graph and lets see what the torque curve looks like compared to A/F. I hope you got one with ZERO smoothing.
You have to see what the VE looks like as RPMs rise. you gave us a low power number which implies low torque, but low torque in the midrange vs low torque after 5krpm is a completely different situation.
You have to see what the VE looks like as RPMs rise. you gave us a low power number which implies low torque, but low torque in the midrange vs low torque after 5krpm is a completely different situation.
03-07-2018, 06:24 PM
#18
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What does the merge pipe look like? Crappy merge will kill power. You could likely benefit from more compression as well.
03-07-2018, 07:06 PM
#20
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I’m thinking it’s cam. It may not fit this combo. Looking at going with Texas speed torquer v2 or maybe tsunami cam. Emailed Texas speed today but haven’t had a reply back yet.