why does power curve get bumpy after 5,200 (centri blower)
Thread Starter
TECH Apprentice
Joined: Sep 2010
Posts: 325
Likes: 0
why does power curve get bumpy after 5,200 (centri blower) I put the car on a different dyno last weekend for a car show and noticed that the power seems uneven over 5,200 rpm. I'm not really that concerned with the peak numbers since weather/dyno/ect were different, but I think it should be carrying the power better up top.
First thing I'm going to check and swap are the plugs, but curious if anyone else has ideas on things to check. I've noticed the low rpm driveability has been a little off lately as well, which seems like it could be a plug thing too.
First thing I'm going to check and swap are the plugs, but curious if anyone else has ideas on things to check. I've noticed the low rpm driveability has been a little off lately as well, which seems like it could be a plug thing too.
Thread Starter
TECH Apprentice
Joined: Sep 2010
Posts: 325
Likes: 0
Thread Starter
TECH Apprentice
Joined: Sep 2010
Posts: 325
Likes: 0
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Thread Starter
TECH Apprentice
Joined: Sep 2010
Posts: 325
Likes: 0
Thread Starter
TECH Apprentice
Joined: Sep 2010
Posts: 325
Likes: 0
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
Sure it isnt just a a fault of the dyno ?
Or possibly excessively fuelled ?
There is nothing on the graph to indicate lean...or a misfire as such. Unless it is mega rich, and that's causing the misfire and a leaner than expected reading...hence a fairly normal AFR reading overall.
Ive 7's in my car, really cant see a need for 8's let alone 9's. Although an 8 would do no harm.
How does the car perform on the street ? With such a flatline, it should be noticeable if there was a problem.
Or possibly excessively fuelled ?
There is nothing on the graph to indicate lean...or a misfire as such. Unless it is mega rich, and that's causing the misfire and a leaner than expected reading...hence a fairly normal AFR reading overall.
Ive 7's in my car, really cant see a need for 8's let alone 9's. Although an 8 would do no harm.
How does the car perform on the street ? With such a flatline, it should be noticeable if there was a problem.
If you want to try a colder plug that seems to fire better in my opinion at that power level on E85 try the NGK R5724-9 stock number 7891. These are non resister "racing" plugs. They will also come with a tighter gap out of the box. I swap out my 7s every 1500 miles, or before each racing event.
Didn't you dyno out a bit higher on HP before, like 915rw? I have seen additional timing help smooth out the graph when it oscillates like that as well, but that depends on where you are at currently.
I'd say its in the ignition, probably plugs, possibly wires.
Didn't you dyno out a bit higher on HP before, like 915rw? I have seen additional timing help smooth out the graph when it oscillates like that as well, but that depends on where you are at currently.
I'd say its in the ignition, probably plugs, possibly wires.
Thread Starter
TECH Apprentice
Joined: Sep 2010
Posts: 325
Likes: 0
Sure it isnt just a a fault of the dyno ?
Or possibly excessively fuelled ?
There is nothing on the graph to indicate lean...or a misfire as such. Unless it is mega rich, and that's causing the misfire and a leaner than expected reading...hence a fairly normal AFR reading overall.
Ive 7's in my car, really cant see a need for 8's let alone 9's. Although an 8 would do no harm.
How does the car perform on the street ? With such a flatline, it should be noticeable if there was a problem.
Or possibly excessively fuelled ?
There is nothing on the graph to indicate lean...or a misfire as such. Unless it is mega rich, and that's causing the misfire and a leaner than expected reading...hence a fairly normal AFR reading overall.
Ive 7's in my car, really cant see a need for 8's let alone 9's. Although an 8 would do no harm.
How does the car perform on the street ? With such a flatline, it should be noticeable if there was a problem.
Car still feels good, but if it's only missing 40-50whp I'm not sure I'd really feel that since it doesn't nose over, just doesn't reach the same peak.
I'm going to stick with the 7's since they did ok before (and I already have spares I've been meaning to swap).
Here's a pen and paper overlay w/ the other dyno hp curve. It's about ~25hp difference for weather/dyno I'd guess, so this should have been ~875whp maybe.
Thread Starter
TECH Apprentice
Joined: Sep 2010
Posts: 325
Likes: 0
If you want to try a colder plug that seems to fire better in my opinion at that power level on E85 try the NGK R5724-9 stock number 7891. These are non resister "racing" plugs. They will also come with a tighter gap out of the box. I swap out my 7s every 1500 miles, or before each racing event.
Didn't you dyno out a bit higher on HP before, like 915rw? I have seen additional timing help smooth out the graph when it oscillates like that as well, but that depends on where you are at currently.
I'd say its in the ignition, probably plugs, possibly wires.
Didn't you dyno out a bit higher on HP before, like 915rw? I have seen additional timing help smooth out the graph when it oscillates like that as well, but that depends on where you are at currently.
I'd say its in the ignition, probably plugs, possibly wires.
That's good to know, I have ~2,000 miles on these plugs. Figured I'd have to change them more often w/ the copper, but wasn't sure what 'often' was. I'll keep those other ones in mind too for the next plug change.
Yea, it did 915whp on Justin's dyno back when it was cold out. I think I'm around 16* advance.
TECH Enthusiast
Joined: Jul 2008
Posts: 577
Likes: 1
From: League City, Tx
First thing I notice is the smoothing is set on 3, that's one reason the chart is so bumpy. Second thing I would do is change plugs, run whatever you want in it but put a fresh set in, regardless of what they look like. I recently ran into a weird running issue that would only occur at wot at high rpms, I found a hair line crack in the porcelain on one plug, it was arcing from that crack to the head. Next thing to check is ohm out the plug wires, especially if you have done a coil relocation... I had a weird miss that would develop at 5000 rpms under boost and it was one spark plug wire (brand new MSDs) that had high ohms, it was a questionable connection. Now I keep extra MSD wire in stock as well as connectors and check my ohms often.
Lastly it "could" be valve springs but I doubt it unless the springs weren't setup to the correct spring height. I have the same cam you do and run a little less spring then you have and mine pulls clean to 7200.... (Although my power peaks at 6000 and holds it to 6400, then starts dropping). Lastly is good ole belt slip.. You'll see that in your KPAs on HPT though if at slipping.
Your combo may not make power at 7000 but it shouldn't nose dive the way if does.. My guess is plugs or wires.
Look at your O2 readings(the factory O2s, not the wideband) on each bank and compare them, make sure they are tracking closely and no weird spikes or dips... If you see something there, its an ignition miss for sure.
Lastly it "could" be valve springs but I doubt it unless the springs weren't setup to the correct spring height. I have the same cam you do and run a little less spring then you have and mine pulls clean to 7200.... (Although my power peaks at 6000 and holds it to 6400, then starts dropping). Lastly is good ole belt slip.. You'll see that in your KPAs on HPT though if at slipping.
Your combo may not make power at 7000 but it shouldn't nose dive the way if does.. My guess is plugs or wires.
Look at your O2 readings(the factory O2s, not the wideband) on each bank and compare them, make sure they are tracking closely and no weird spikes or dips... If you see something there, its an ignition miss for sure.
TECH Enthusiast
Joined: Jul 2008
Posts: 577
Likes: 1
From: League City, Tx
One more thing, try making a pull without the inlet pipe/air filter on the blower and I bet that smooths out the curve and makes it hold on better.. My curve looks similar to yours until I pulled off the filter/pipe, I made no other change and it gained 45 HP and the curve was better, as you can see in this pic:
F series blowers don't like anything on the inlet.
F series blowers don't like anything on the inlet.
TECH Enthusiast
Joined: Jul 2008
Posts: 577
Likes: 1
From: League City, Tx
Your Dyno guy needs to give you the numbers in SAE and Smoothing set on 5. Stick with the AFR you're seeing in your wideband, not the tail pipe sniffer. 10.6 is pretty rich.. I went from 10.6 AFR to 10.9-11.0 AFR and it gained 40rwhp. So maybe your tune is getting off some how, maybe the O2 sensors are getting wacked..
I also run the BR7EF plugs with no issues.. Just keep em fresh regardless of from the plug reading is showing you.
In theory, SAE will correct the numbers (to a degree) for crappier weather etc etc.. Yes you'll make more power in better air, but you'll have less correction factor adding in to the numbers so they should always be similar..(assuming same Dyno and SAE correction.
I also run the BR7EF plugs with no issues.. Just keep em fresh regardless of from the plug reading is showing you.
In theory, SAE will correct the numbers (to a degree) for crappier weather etc etc.. Yes you'll make more power in better air, but you'll have less correction factor adding in to the numbers so they should always be similar..(assuming same Dyno and SAE correction.
