Diagnose this bad pull

x MadMAX DIESEL

<<<< No Horsepower
Dec 30, 2008
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Lexington, Ky
I know blow by is just the nature of the performance engine. It's not a big deal I don't care about it. Though I don't like the irractic pressure.


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dirty_max

Member
Jan 27, 2013
815
2
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eureka il
I tend to disagree on this a bit. If you have a boost leak the chargers will overspin running way out of their map to achieve set amount of boost. Generally speaking a leak will cause them to still make the same boost #'s on a gauge but having to work 10 times harder and out of their operating range to do it. Just my experience. ...

if this is true it would achieve this by throwing more fuel at it, why is it clearing up so much then? leak on exhaust side or compressor side would cause more smoke. I agree that they will overwork themselves to get there but they cant just decide they want to spin faster, they have to have more fuel to do it, but if its still making the same amount of air why would it matter it it is being overworked?
 

dirty_max

Member
Jan 27, 2013
815
2
18
eureka il
compression and blow by dont go together. just cause you have low compression pistons doesnt mean you should be experiencing alot of blow by. rings, valves, and HG dont care what the compression is of the pistons. if those dont seal, you get excessive blow by. if you setup the ring gaps to be loose and the piston to sidewall to be loose, that can create more blow by than factory.

this is sort of what im getting at. yes with a high horsepower engine you will have more blowby, but there is still a ratio to go by. typically its about 1to1 with horsepower. so if you have an 800 hp engine it should have approximately 800 cubic feet/hr. blowby. im not saying you are wrong but I thought compression did affect blowby a little bit. that's how we would figure out if an engine was worn out, we would stick it on the dyno and do a hp/blowby run and compare the numbers to see if an overhaul was needed. and in this case, lower compression would result in lower blowby unless its supposed to be pushing past the rings. sorry if any of this is confusing, im speaking more from a stock diesel engine standpoint, but I believe the fundamentals are still the same. if you could get your truck on a dyno and do a hp/blowby test, I would think that should tell you a little bit more of the story rather than visual inspection and a compression test while its cold.
 

IdahoRob

New member
Jun 5, 2007
1,151
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If your data logs are showing constant timing, fuel pressure, and injection flow rate throughout the pull, then it is not ecm/tuning issue causing the problem. It is mechanical. Could be engine, turbos, etc. I'd do a compression check before anything. Next would be a pressure test on the whole intake side of things.
 

PureHybrid

Isuzu Shakes IT
Feb 15, 2012
3,496
480
83
Central OH
Drive up to IN and have Danville or Fleece dyno tune that thing.

Didn't you have trouble when it was a stock motor/turbo truck too?
 

x MadMAX DIESEL

<<<< No Horsepower
Dec 30, 2008
7,535
1
38
34
Lexington, Ky
Drive up to IN and have Danville or Fleece dyno tune that thing.

Didn't you have trouble when it was a stock motor/turbo truck too?

That trouble was because the tuner (who I won't mention but isn't around anymore) didn't know you had to add Baro to the boost. So the 30psi would be like 15 lol. But I think I've got it figured out now
 

Bonestock

Active member
Aug 9, 2010
1,358
1
38
Worland Wy
if this is true it would achieve this by throwing more fuel at it, why is it clearing up so much then? leak on exhaust side or compressor side would cause more smoke. I agree that they will overwork themselves to get there but they cant just decide they want to spin faster, they have to have more fuel to do it, but if its still making the same amount of air why would it matter it it is being overworked?

You are correct on needing more fuel and causing more smoke. Turbos all have MAPS that they are designed to run in to provide optimum effeciency and output. Once you overspin the charger running it out of its map your output can still achieve set amount of boost but will not run anywhere near the same if it were operating within its map.

Glad you found your problem hope you go win some pulls!
 

JoshH

Daggum farm truck
Staff member
Vendor/Sponsor
Feb 14, 2007
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Texas!!!
I did that on my truck and never had that problem. That's pretty wild.
 

x MadMAX DIESEL

<<<< No Horsepower
Dec 30, 2008
7,535
1
38
34
Lexington, Ky
It musta been like 40k. I that's why I wish I could rescale the sensor, I'd get a big one right away. I actually blew a check ball out lastyear, but didn't have this exact problem.


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