Kennedy (or anyone)...My boost spikes to 16?

[DennisG01]

I have had John's electronic boost booster installed for a few months now and have been happy with the way he sent it to me at the "mild" setting. I just had a boost gauge installed and I am getting boost spikes on acceleration up to about 16 psi. (I have not played with the booster, yet) Is this normal? JK's website says max boost is in OD, 2200-2500rpm, max pedal pressure w/o converter unlock or downshift. I'm going to go out and get on the highway right now to check that. I was just wondering about the spiking thing?

after the highway drive (running about 2300 rpm with pedal depressed quite far - I never detected the converter unlocking):

w/o electronic boost control: 9 psi.
w/ electronic boost control: 14psi.

[ 08-12-2004, 04:00 PM: Message edited by: Dennis Galligani ]

[MTTwister]

Dennis - I made my own - 10K linear pot, with the "boost" side set to 2K resistance. I've seen spikes to 13#, with EGT's @ 900

[charliepeterson]

I have one of John's old style sensors and it has a very small adjustable screw on it. The high boost numbers without an inter cooler really isn't a good idea.

[whatnot]

I don't think the boost spikes hurt anything. The air won't get hot that quick so an intercooler wouldn't make that much difference. (Talking about for the boost spike, not intercooler in general)
It is the sustained boost that you need to look at.
If you don't want the high spikes, get a turbomaster. But you will get a puff of black smoke out the tailpipe instead.

[DennisG01]

I'm leaving for vacation in a few minutes. I'll keep an eye on EGT. As long as no one thinks the spikes are a bad thing, I feel OK. On a downside, since the Electronic Boost came from JK set at the "mild" setting, I was looking forward to 'turning it up a notch'. Looks like I can't do that now - as I'm already getting 14psi. Maybe I'm not checking it correctly?

[whatnot]

It shouldn't have "notches", it is variable. You should be able to set it wherever you want to.

You can remove it and see what the gauge reads with the stock setting. I believe they usually spike around 12 psi and then settle around 6 psi.

[Kennedy]

EGT's will be low with that much boost.

If you watch the tach, I'm sure it is at 2k or even less. Basically, the ECM flat ines duty cycle at 100% until the RPMs cross 2000 where it starts to actively modulate vacuum.

You should be in good shape. If nothing else, drop the srcew 1/2 turn counterclockwise.

[jspringator]

I have the style with the small screw. I recently turned mine up for a trip and noticed the EGT'S were lower than past trips. If the intake temps get too high the computer will cut fuel, but am I correct in believing that until that happens, high boost is ok with low engine temps and low EGT'S?

[MTTwister]

Excellent question - I'd like to know, too - When is too much boost - too much boost. Blow the heads off and then back off 2#'s?

"I have the style with the small screw. I recently turned mine up for a trip and noticed the EGT'S were lower than past trips. If the intake temps get too high the computer will cut fuel, but am I correct in believing that until that happens, high boost is ok with low engine temps and low EGT'S?"

[rjschoolcraft]

So far, more boost equals lower EGT. That was true even without the intercooler, except it couldn't sustain it because IAT would go up, the computer would cut fuel, boost would fall and temps would rise.

With intercooler, more boost equals lower EGT. I haven't found the limit yet at 18 psi sustained at 800 ft above sea level. I'm running out of turbocharger, though, and am hesitiant to increase boost any further until I can build an 18:1 engine and upgrade the turbocharger.

[jspringator]

Good to hear from you, Ronniejoe. I have a new 9,000 pound trailer since last we met, and I am afraid the weight has destroyed my torque converter, After that is resolved, I am going to have to go the intercooler route to pull that kind of weight.

[Marlin]

James,
How do you know that your torque converter is going bad? What are the symtoms?
Thanks,
Marlin

[jspringator]

I don't hear anything while idling, but when going about 35 mph with windows down I hear a rumbling clanging sound. I haven't had it diagnosed for certain, but I am preparing for the worst.

[ 08-14-2004, 07:43 AM: Message edited by: James Springate ]

[Dvldog 8793]

Howdy
I have the small screw JK controller. Never changed it from what he sent. I see 15-16lb spikes that fall to a sustained 12lb. In my mind the spike is not important as it falls almost instantly. My EGTs never get above 800. so far I have not had the need for an intercooler, but I do have about half of a really nice liquide system sitting on the shelf. JUST IN CASE! :D
L8r
Conley Janssen

[DennisG01]

Thanks, everyone. OK, here's what I got on the ~500 mile trip from PA to ME (I'm pulling a 6,000lb. boat - me, wife, 3 month old and Labrador in Suburban).

EGT's: usually around 550-650, occasionally to 860 (pre-turbo), as low as 450.

Max sustained boost, at about 70 mph and 2100rpm: 14-15#'s.

how do those numbers sound? should I turn the boost screw up/down/leave it alone?

[rjschoolcraft]

I would leave it alone. If you tow anything heavy, you will start to see the computer pull fuel. You will likely need an intercooler in that event. If you don't tow anything heavier than what you currently do, you will probably be fine.