MPI Twins questions

lcaad1249

lcaad1249

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Jun 6, 2007
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Thanks to Bad-Duvall and a few friends, we finally got my MPI twins on today. The set is a 66/71/13 SS over an S480 with a race cover and an external wastegate around the primary. This is OT-Of-Here's old set of twins. The turbos were rebuilt though due to the coolant in the oil. I've got a few questions. We had to wire the wastgate on the 66 shut for now and get one of the springloaded wategate from Nathan.

First of all, My EGT's are higher than I expected. I've already seen 1300 degrees. Pat said he never had EGT issues on his truck. Is this due to the newly rebuilt turbo's? Or with my stock injectors do I not have enough fuel to keep cool everything down yet? Not sure if that makes sense.

Second question, how does the springloaded wastegate controller work without a boost reference??

Third of all, I don't think anything would need to be changed from Pat's setup to mine, but how would I know where the optimal external wastegate setting be?

I'm sure I've got more questions, but it's been a long day.

Thanks in Advance!
 
those springloaded wastegates are complete junk, what settings were you at when you saw the 1300? and is that at WOT or just cruising around?
 
Part of the egt issue could be because of the wastegate being wired shut but there are way too many possible causes like low rail pressure, too much duration, or wastegate issues. I doubt it was because the turbo's were rebuilt.

For the time being run full boost from the manifold to the top of the external wastegate (the bottom how it is mounted in the truck) and nothing to the bottom. This will rule it out as a possible issue (unless it is stuck open). Then back off the spring on the 66 wastegate so it has a maximum travel of about 3/16". Make sure you keep an eye on rail pressure when you run the truck and don't run the TST higher unless it stays above 20k or so. That should keep your egt's in check.
 
TMONEYDIESEL said:
those springloaded wastegates are complete junk, what settings were you at when you saw the 1300? and is that at WOT or just cruising around?
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Why are springs complete junk and what would be a better solution?
 
Also that is a pretty laggy set of twins and getting ahead off the egts can be difficult. I bet your wot egts arn't much higher than 1300 huh.
 
Idaho CTD said:
Part of the egt issue could be because of the wastegate being wired shut but there are way too many possible causes like low rail pressure, too much duration, or wastegate issues. I doubt it was because the turbo's were rebuilt.

For the time being run full boost from the manifold to the top of the external wastegate (the bottom how it is mounted in the truck) and nothing to the bottom. This will rule it out as a possible issue (unless it is stuck open). Then back off the spring on the 66 wastegate so it has a maximum travel of about 3/16". Make sure you keep an eye on rail pressure when you run the truck and don't run the TST higher unless it stays above 20k or so. That should keep your egt's in check.
Click to expand...

Right now I'm only running the Smarty TNT Revo and EZ on the lowest setting. TST hasn't been turned on. I seem to have good rail pressure although I can say I can't watch too much while the big turbo hits. WOW!! I can't run at WOT yet but I haven't seen over 1300 but thats also mainly cruising. We'll be installing head studs, injectors, valve springs, and dual CP3's later this week.

One other wierd thing I noticed was that I installed 2 EGT probes, one for the TST and one for my SPA gauge. The SPA is in the front half of the manifold and the TST is in the back. Seem pretty close temps at idle but cruising can be about 200 degrees warmer in the front half.
 
I half a lot more fuel than you and I dont have temp issues. My secondary is much smaller as well
 
I was sure Pat had a 64....

Its going to be laggy on the bottom I imagine, there will be a good "dead band" that you have to come through before you get on top of the egt's.

Bigger sticks (and pumps) would get you through that band faster, but you'll always see higher egts when cruising or low to low mid power. Nature of the beast with big turbo's.
 
Anthony glad to see you finally got them chargers on. Maybe I should bring my truck over to Duvall's so he can wrench on mine to.HAHAHa Actually starting to get tired of wrenching on mine just don't let Ben hook up your dual pumps. Just kidding.
 
lcaad1249 said:
Right now I'm only running the Smarty TNT Revo and EZ on the lowest setting. TST hasn't been turned on. I seem to have good rail pressure although I can say I can't watch too much while the big turbo hits. WOW!! I can't run at WOT yet but I haven't seen over 1300 but thats also mainly cruising. We'll be installing head studs, injectors, valve springs, and dual CP3's later this week.

One other wierd thing I noticed was that I installed 2 EGT probes, one for the TST and one for my SPA gauge. The SPA is in the front half of the manifold and the TST is in the back. Seem pretty close temps at idle but cruising can be about 200 degrees warmer in the front half.
Click to expand...

That happens. I have three egt probes (one for TST, one for the autometer guage and one for the snow water/meth) two are mounted in the pre-drilled positions on the ATS manifold which is one for the rear 3 cylinders and one for the front 3, both down at the collector and the last one on the top nearest cyl 5. I noticed that the front was always about 100* warmer so I swapped all the probes around until each had a turn at each position. I found all 3 probe to be remarkably similar in the readings and all read the first three cyls. as being hotter which is the opposite of conventional wisdom.

I'd say, based on my experience that is accurate.
 
soulezoo said:
That happens. I have three egt probes (one for TST, one for the autometer guage and one for the snow water/meth) two are mounted in the pre-drilled positions on the ATS manifold which is one for the rear 3 cylinders and one for the front 3, both down at the collector and the last one on the top nearest cyl 5. I noticed that the front was always about 100* warmer so I swapped all the probes around until each had a turn at each position. I found all 3 probe to be remarkably similar in the readings and all read the first three cyls. as being hotter which is the opposite of conventional wisdom.

I'd say, based on my experience that is accurate.
Click to expand...

I made another interesting discovery. I just installed an AFE Bladerunner yesterday and only have about 10 miles on it, but my back 3 cyliinder temperatures stayed roughly the same as before but reduced the front three down about 400 degrees at WOT.
 
Ok so what are the temps then? a 400 degree difference seems like a lot.
You mean your back three are running say 1400 and your front running 1000?
Thats pretty weird.......

How about some boost numbers?
 
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Joesixpack said:
Ok so what are the temps then? a 400 degree difference seems like a lot.
You mean your back three are running say 1400 and your front running 1000?
Thats pretty weird.......

How about some boost numbers?
Click to expand...

I mean it cooled down the front three 400 degrees. Like instead of the back three being at 1000 and the front being at 1200 the front three are now at 800. It's kind of hard to pay attention to everything but that was probably around 50 pounds of boost. It will hit 70 easily.
 
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