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Performance Tuning for the Tahoe

6.2 turbo

6.2 turbo

Well-Known Member
Messages
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Location
pa
I'm going to post all my tuning efforts here. So far I have driven about 10 miles,and currently the engine is getting new head gaskets. Here are some observations while it was running. The axle gearing feels plenty high,3.42's. The converter feels plenty loose also. The torque converter lock up slips while engaging under full power. The injector pump is a stock db2831,with the screw tight. The advance screw is turned out very far,this is how it was. With my high compression,it seems to be getting to much timing. I bought a Snap On MT 480,but I'm missing the glow plug adapter. With a temporary boost gauge it made 25 psi, but never lit. It spooled gradual ,but never felt lag either,thanks to a very high factory stall converter. Also it hits the governor early,and cuts fuel,not real far beyond the stall speed. No tach yet. From a dead stop there was only a puff of smoke. Lugging it in 3rd it smoked a fair amount. Free revving also got a fair amount of smoke. At idle the exhaust smells like a newer diesel,I think this is from the compression ? Also my lift pump is cavitating. I'm pretty sure that some governor work will make it come alive. Sounds to easy don't it ?
 
6.2 turbo said:
I'm going to post all my tuning efforts here. So far I have driven about 10 miles,and currently the engine is getting new head gaskets. Here are some observations while it was running. The axle gearing feels plenty high,3.42's. The converter feels plenty loose also. The torque converter lock up slips while engaging under full power. The injector pump is a stock db2831,with the screw tight. The advance screw is turned out very far,this is how it was. With my high compression,it seems to be getting to much timing. I bought a Snap On MT 480,but I'm missing the glow plug adapter. With a temporary boost gauge it made 25 psi, but never lit. It spooled gradual ,but never felt lag either,thanks to a very high factory stall converter. Also it hits the governor early,and cuts fuel,not real far beyond the stall speed. No tach yet. From a dead stop there was only a puff of smoke. Lugging it in 3rd it smoked a fair amount. Free revving also got a fair amount of smoke. At idle the exhaust smells like a newer diesel,I think this is from the compression ? Also my lift pump is cavitating. I'm pretty sure that some governor work will make it come alive. Sounds to easy don't it ?
Click to expand...

:popcorn::nopics: we are watching this closely... make sure your camera is charged too...LOL... are you going to use your larger stanadyne fuel inlet as well? do you have a line on stanadyne pieces? we would like to find a set of .370 plungers, that are ceramic coated.... what do you think about the plunger mod that your machinist does? is it a quality mod, or is it a bit lacking? what does he use for plunger material? does he ceramic coat them? anyways we are looking forward to your over-the-top pump mods in the quest for 60psi boost...LOL...... and i am looking forward to knowing your first name as well...LOL... when there are no caps, its me the jeff typing...
 
There was a local place that could get me pretty much any Stanadyne part. But they are no longer in business . Davies Machine does excellent work. I would recommend chrome plating,don't think ceramic will work. I did notice the rollers from a DS4 are lighter,and grey colored. I think they are titanium ? They will fit a DB2. What I would like to do sometime ,is get a head and rotor machined,and then send it to CPQ- Diesel Doctors,and get it chrome plated. For now I will work with what I have. Once it is running again I'll try to video free revving smoke. Then I will do it again when there is more smoke. Might do some 0-60 videos also.
 
Adjusted the bottom timing lever screw in 3 turns. I might try locked timing at some point,I don't think it will be as much of an issue,like my 6.2 . Low compression needs more timing ? I'm going to let the governor alone until I get a tach working.
 
Ha good thinking, I would hate to not have a tach.

What screw are you referring to? The one on the advance arm at the bottom that pushes against the advance piston?
 
Eh...... yea i will do that! My dad an bro an i have a shop in Spring Grove Pa an we are really busy so i just read wen im taking a break or over lunch an never take the time to fill out my sig!!!
To 6.2 , keep up the mods , i love your thinking! Sometime we needa meet up to swap drinks an ideas!!!
 
hey 6.2 i got my pump off and turns out its a 5068 instead of the 5288 that you have ripped apart, wich aparently they claim the 5068 is the heavy duty pump, so mabe these plungers are a bit bigger, idk. i have a rebuilt pump ordered so we can tear mine apart if your interested. looks like the metering valve and spring are fine so must be the electronics? i can drop those parts off some night after work since i aint gonna use them after all. ill give ya a call sometime i got an evening im not busy.
 
My fuel pressure is very erratic. I set it at 30,and it went to 40,and it also went to 10 ,after a long pull. The I blame the china regulator. I think I will dead head,and try that.
 
I backed the advance screw out 1 turn,timing is still on the verge of being retarded. I lowered the fuel psi to 20,it stayed very stable. I now have aworking tach,so I installed a solid governor. Stock was 3500,now it can go 4000,but struggles,at that point. Fuel output increased,but not enough Then I cranked the external regulator tight,and changed the internal spring in the Holley pump. Now lift psi is 15. It seems to rev easier now,but fuel output stayed the same. The reason for deadhead,was 8 psi in the return line. I don't now what a normal 4l80-e stalls at,but mine is 2000rpm,brake torquing,and 3000 rpm,any time in 3rd gear. I hate it,but will leave it be untill I get the horsepower increased. Not so sure about the turbo either,it still will not light,it almost will in second with the tcc locked . Max boost is still only 25 psi. I'm afraid I have a combination of lots of wrong parts. Gearing, torque converter,turbo,and ip,these are all prime suspects. Not to sure if the 4l80-e is not killing the motor, all by it self .
I probably should check turbo drive pressure,because of not being able to rev past 4000 rpms, this not a good sign of very great exhaust flow. The stock ip is going to come off shortly,not sure if I will bother tweaking it more. There is still some more fuel left in it,but probably not enough any how. I'm leaning towards yanking the 4 plunger off of the 6.2. If that pump can't light the turbo,I will put another identical turbo on. The compressor wheel is not in very good shape,but did make over 60 psi on a Cummins 5.9.
 
6.2 turbo said:
I backed the advance screw out 1 turn,timing is still on the verge of being retarded. I lowered the fuel psi to 20,it stayed very stable. I now have aworking tach,so I installed a solid governor. Stock was 3500,now it can go 4000,but struggles,at that point. Fuel output increased,but not enough Then I cranked the external regulator tight,and changed the internal spring in the Holley pump. Now lift psi is 15. It seems to rev easier now,but fuel output stayed the same. The reason for deadhead,was 8 psi in the return line. I don't now what a normal 4l80-e stalls at,but mine is 2000rpm,brake torquing,and 3000 rpm,any time in 3rd gear. I hate it,but will leave it be untill I get the horsepower increased. Not so sure about the turbo either,it still will not light,it almost will in second with the tcc locked . Max boost is still only 25 psi. I'm afraid I have a combination of lots of wrong parts. Gearing, torque converter,turbo,and ip,these are all prime suspects. Not to sure if the 4l80-e is not killing the motor, all by it self .
I probably should check turbo drive pressure,because of not being able to rev past 4000 rpms, this not a good sign of very great exhaust flow. The stock ip is going to come off shortly,not sure if I will bother tweaking it more. There is still some more fuel left in it,but probably not enough any how. I'm leaning towards yanking the 4 plunger off of the 6.2. If that pump can't light the turbo,I will put another identical turbo on. The compressor wheel is not in very good shape,but did make over 60 psi on a Cummins 5.9.
Click to expand...
the pump on your 6.2l is the one that you built with the db-4 head and rotor? which turbo are you going to use? i am glad that you got your head gaskets to seal again...
 
Yes the 6.2 has the .310 x 4 plunger . I will leave the hx 52 on untill I'm sure it is getting plenty of fuel. I think something is actually wrong with ip,possibly one plunger is stuck. Charge pressure is still stock,and the limiter spring is still there also. It feels like it still has a governor,maybe the JB weld broke. It also sounds like an injector randomly leaks at idle. A fairly lound knock on one cyl,but clears up,after reving it. I'm not to worried about that,it might heal itself. I did put 2 onces of Stanadyne aditive in the tank.
 
Does it smoke alot? Is that 25 psi at full throttle?

I think possibly to exceed 4000 rpm well, a much better exhaust is needed than what GM provided us with. I would be interested to see what the drive pressures are.
 
It does not smoke much,seems to clear up around 10 psi. 25 psi is not untill 3000 rpms,it doesen't even need that much at that point. I think my 92 smoked more than the Tahoe,with a stock pump,but the limiter spring was removed on that one. Also the 92 is stick shift . Probably my Tahoe runs a lot better than stock,but seems dead to me. I'm a bit bafled that it don't run better with the ip thats on. It could also be that the high compression is clearing up smoke,on its own,and there's no fuel left to light the turbo? How confusing is that ? All the therories that work on paper,totally change in the real world .
 
Like you said before, gearing probably has a lot to do with it, lower gear ratio and the 4l80e could be making a good size difference.
 
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