The Official 1HD-T/FT Fuel Pump Mod Tuning Thread (2 Viewers)

[DancesWithMutts]

I need to run something by you guys.

With my current tune, the only time I get high in temps is when I am getting the revs above 2700 or so in 3rd gear (auto). From what I read, most peoples EGT's drop when they down-shift into 3rd.

I keep thinking I should try and advance the timing a little bit, what do you think?

Edit: I should say that I am still holding boost just fine. I'm also running a HPD front-mount.

 

[Tapage]

From what I read, most peoples EGT's drop when they down-shift into 3rd..

EGT's are direct relation between engine load, fuel, intake temps, and boost / oxygen not that simple like down shift ..

 

[IanB]

EGT's are direct relation between engine load, fuel, intake temps, and boost / oxygen not that simple like down shift ..

Engine load definitely changes if you're climbing a long grade in 4th and downshift to 3rd, on the '93+ HDJ81's with the electronic A442F you have TC lockup in 3rd as well as in OD/4th, so the revs go up, and the EGT's do come down, in my experience.

 

[DancesWithMutts]

EGT's are direct relation between engine load, fuel, intake temps, and boost / oxygen not that simple like down shift ..

I can't go over 3K without EGT's climbing past 1300, and quick. The idea that my timing is retarded and I am venting still burning fuel makes a lot of sense to me.

I can hit that magic sweet spot where I am holding 4th, putting down peak horsepower and my temps are around 1150, but If I lose speed and have to downshift, It's game over.

Do I have anything to lose by trying?

 

[IanB]

I can't go over 3K without EGT's climbing past 1300, and quick. The idea that my timing is retarded and I am venting still burning fuel makes a lot of sense to me.

I can hit that magic sweet spot where I am holding 4th, putting down peak horsepower and my temps are around 1150, but If I lose speed and have to downshift, It's game over.

Do I have anything to lose by trying?

Just your time.

 

[DancesWithMutts]

I did a little more "scientific" testing. This thing HATES to rev over 3k. Here are my findings.

Pretty steep hill. Armored but empty HDJ on 285's

4th gear
2200rpm
95kph
1010 degrees EGT
15 psi boost

I then turned around and pulled the exact same hill again keeping my speed the same.

3rd gear
3000 RPM
95kph
1290 EGT
14.2 psi boost.

Does that sound right to you guys?

 

[SeaJay]

is it starving for air? is your air filter clean? is it the factory air cleaner and hose from air cleaner to turbo?

 

[mudgudgeon]

Auto or manual trans?

What turbo?

Are you saying it WONT rev above 3k, or that EGTs come up too high above 3k?

 

[DancesWithMutts]

is it starving for air? is your air filter clean? is it the factory air cleaner and hose from air cleaner to turbo?

Safari snorkel, stock airbox stock hose, cleanish filter. Hpd front mount, stock turbo stock exhaust.

Auto or manual trans?

What turbo?

Are you saying it WONT rev above 3k, or that EGTs come up too high above 3k?

Auto, stock turbo. It will rev above 3k but with any kind of real load the EGT's (pre turbo) are just too high.

Another funny thing is that the HPD front mount intercooler made very little impact on my EGT's, which also makes me wonder about retarded timing.

 

[IanB]

I would have expected the 3rd gear run to have at least the same boost level as the 4th gear run, and for EGT's to be lower in 3rd.

The fact these are your results and you have an intercooler are puzzling.

Factory exhaust will be a real choke point, is that something on your to-do list?

Snorkel could be a restriction, is there a simple way to disconnect and re-test to rule it out?

 

[DancesWithMutts]

I would have expected the 3rd gear run to have at least the same boost level as the 4th gear run, and for EGT's to be lower in 3rd.

The fact these are your results and you have an intercooler are puzzling.

Factory exhaust will be a real choke point, is that something on your to-do list?


Snorkel could be a restriction, is there a simple way to disconnect and re-test to rule it out?

Yes, hopefully in the next couple of weeks. While I've got everyone's attention, can I fit 3" into the factory exhaust path?

I'll check out the snorkel.

 

[Lumpskie]

Safari snorkel, stock airbox stock hose, cleanish filter. Hpd front mount, stock turbo stock exhaust.



Auto, stock turbo. It will rev above 3k but with any kind of real load the EGT's (pre turbo) are just too high.

Another funny thing is that the HPD front mount intercooler made very little impact on my EGT's, which also makes me wonder about retarded timing.

With you living above 5000 ft, I bet your stock turbo is running out of air. On my Evo, I had the stock turbo suck hot air and run out of gas at high RPMs, when I lived in Colorado.

 

[IanB]

Yes, hopefully in the next couple of weeks. While I've got everyone's attention, can I fit 3" into the factory exhaust path?

I'll check out the snorkel.

Better yet, you can run 3" inside the frame rail, it's tight past the transfer case, but it stays tucked up high with less bends than factory routing.

 

[mudgudgeon]

Yes, but you'll get a far better result if exhaust stays to the inside of the frame rail
Far fewer bends, far straighter bends (mostly 45degrees vs 90degrees) far less restrictive, simpler install in some ways, but takes a little more imagination (perhaps).

Have a look at my turbo build thread in my signature, also check out @Dork "mail order ride" thread

With stock exhaust, stock turbo, you'll start running out of legs around 3k, you should be able to push it a bit more, but I think from memory 3200RPM was the rated "peak power" (may be 3600rpm)

On my HDJ81, 3" exhaust, and stock turbo at 18psi (unrecommended) it would rev fairly freely to about 3500, after that, I could rev it to redline but power dropped off fairly fast.

 

[Lumpskie]

Like other guys have said, I run my exhaust inside the frame rail. I went 2.5", because it was cheap. But 3" would fit in there just fine.

 

[DancesWithMutts]

Yes, but you'll get a far better result if exhaust stays to the inside of the frame rail
Far fewer bends, far straighter bends (mostly 45degrees vs 90degrees) far less restrictive, simpler install in some ways, but takes a little more imagination (perhaps).

Have a look at my turbo build thread in my signature, also check out @Dork "mail order ride" thread

With stock exhaust, stock turbo, you'll start running out of legs around 3k, you should be able to push it a bit more, but I think from memory 3200RPM was the rated "peak power" (may be 3600rpm)

On my HDJ81, 3" exhaust, and stock turbo at 18psi (unrecommended) it would rev fairly freely to about 3500, after that, I could rev it to redline but power dropped off fairly fast.

I'll have to get under and look at the routing again.

Mine pulls much harder at 2300 than it does at 3k, letting it shift up to 4th at 3k always gives me a boost in acceleration. I just keep coming back to "it doesn't have enough time to burn all its fuel at higher RPM"

 

[mudgudgeon]

Stock peak torque is at something like 1800rpm, it's torque that makes an engine "pull". The further RPMs climb above peak torque, the less pull you feel.

I would get your exhaust out of the way before changing timing.
Improving exhaust flow is one of the major low hanging fruit upgrades. It will make a big improvement to the truck right across the rev range IMO.
Tick it off, then go looking at more technical adjustments.

 

[IanB]

Mine pulls much harder at 2300 than it does at 3k, letting it shift up to 4th at 3k always gives me a boost in acceleration. I just keep coming back to "it doesn't have enough time to burn all its fuel at higher RPM"

When you shift to 4th at 3K rpm, you should be above ~85km/h so the trans will shift and lock up the torque converter almost immediately, if you aren't paying attention you probably wouldn't even notice it happening, but on my truck when the TC locks up it pulls like a freight train as the trans isn't slipping anymore. My point is there could be more going on contributing to the "seat of the pants" feel than you realize.

 

[DancesWithMutts]

I would get your exhaust out of the way before changing timing.
Improving exhaust flow is one of the major low hanging fruit upgrades. It will make a big improvement to the truck right across the rev range IMO.
Tick it off, then go looking at more technical adjustments.

Good points, I've really been dragging my feet on the exhaust, but I just need to get it done.

When you shift to 4th at 3K rpm, you should be above ~85km/h so the trans will shift and lock up the torque converter almost immediately, if you aren't paying attention you probably wouldn't even notice it happening, but on my truck when the TC locks up it pulls like a freight train as the trans isn't slipping anymore. My point is there could be more going on contributing to the "seat of the pants" feel than you realize.

Ah the lockup, that's the immediate surge I feel. Maybe we can get a group buy going for wholesale automatics valve body's

 

[Tapage]

as general rule ( not taking TC in the equation ) down shift will ease load on your engine .. less load, less boost while you might reduce your speed ( other conditions involved here ) you might increase rpm to keep up to speed which make an impact in exhaust flow ( hot exhaust ).