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2G Throttle Body/Turbo Selection

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AntmanAndLittleDi

Proven Member
161
15
Nov 12, 2014
Russell, Kansas
We'e having a few problems with our car, mainly the turbo giving out (whistling with shaft play) and hunting a possible vacuum/boost leak. The car drives great, but it'll lose power (I'm assuming boost) at 4500-5000 rpms, buck, surge and never recover to push beyond that point. This is while driving, but just sitting in the driveway it'll rap 8k rpm without hesitation. We'll hunt the boost/vacuum problem, done it before, many times LOL. My question is mainly regarding the choice of turbo versus the throttle body. We have a large spool 16g turbo that (without looking and I may be wrong) has a 62mm exhaust and an aftermarket BBK throttle body that is still at stock size, about 58mm. I'm curious about the offset size. Is it correct to create a little back pressure on the turbo like this? Or did I just kill the turbo by doing so? The turbo only has about 5k miles of moderate drive time on it. I'd like to get a N/A throttle body since they're at 60mm, but at the same time I can find a 70mm for $90. What setup should I be looking to accomplish? Back pressure it a little (like 62mm turbo exhaust and 58-60mm TB)? Or no back pressure (go with 70mm TB) at all? I'll also be researching waste gate and blow off valve sizes in the same manner. The bov recirculation line is also set to atmosphere instead of actually recirculating it, not sure if that could cause my problem? It's been that way since we bought the car 4 years ago, but didn't have this problem until recently. My only CEL is for the catalyst system (it's been removed but not deleted out of the ecu) and occasionally one for the fuel rail(?). It has the stock fuel system and injectors (450cc). I have NGK plugs that show signs of running lean, but my wideband averages 14.7 at idle and cruise and drops to 10.2 in pulls. I do have a few mods done, they're all posted in my journal. I'm mostly interested in the turbo/throttle body selection, but feel free to ask questions about the other problem at hand. I've read a few other posts on the problem and have a checklist of things to check, just figured I should make sure I have the right setup to begin with or all my checks will be worthless. By the way, I saw it once and can't find it again, can someone please post up the home boost leak testing kit? The one that you can build with a bike tire pump. Cause I have one of those! Lol
 
I read through the fuel cut symptoms, described as hitting a wall, that's not what I'm experiencing at all. Mine is a stutter with violent bucking or surging. (Kiss your coffee in the cup holder good bye.) It feels very similar to a massive boost leak, which we fought after we bought the poor thing 4 years ago. However I do have the common denominator of stock injectors and stock Maf sensor. We had planned on doing speed density with a Maps system in the future. Tomorrow will be decent weather here and no wind for once so we'll at last be able to look for boost and vacuum leaks. To be proactive, I bought 50ft of new vacuum line. Lol And it just so happens to be the same size as my 490hp camaro, so two birds with one stone. I haven't read all 2330 posts on the first link, but that'll be my bedtime story for the evening, make sure I don't miss anything. Thanks for the quick reply.
 
Got all the vacuum lines replaced except the ones behind the intake manifold. Didn't feel like removing the intake to fit my hands back there. Almost all of them had splits or pinholes and the ones that weren't damaged were so dry they kinked when they were bent. The throttle response increased as well as the rpm range until the stutter, but it still does it. Need a boost leak tester for sure. Found out the throttle body has a paper fiber gasket on the intake side and a metal gasket on the exhaust side. Gonna continue the search for the home blt kit.
 
https://www.amazon.com/Torque-Solution-Boost-Leak-Tester/dp/B014M1LWC2

What temp plugs you running and what gap are they at? Also your throttle body should have oem gaskets and i've never heard of any throttle bodies using a metal gasket to seal. The 10.2 on pulls seems to be the ecu flooding it to attempt to account for the extra air flow. Do you have a mbc hooked up? If so, turn it so it's very low boost then start raising it again after you check that.

Also, you're saying your 16g has a 62mm exhaust wheel?
 
Looking at the NGK website, mine are the platinum plugs that have a heat range of 6. When I picked them up from the parts store the clerk said they were pre-gapped, but the website says nothing about that, says they need 1mm gap. Add that to the checklist to double check. As for the gaskets I've already hunted down a set of both, having mix-matched didn't settle right with me. If 10.2 is too much, what should I be aiming for? The number I've seen most often is 10.5 so I assumed 10.2 was pretty close & didn't worry about it. There is a mbc, it was set to 16psi at the factory and we haven't messed with it, may start to now LOL. And since you asked specifically, I looked up the specs for my turbo and I was wrong, it's 58mm also.
 
So the oem plug heat range, that is good. Yea they are "pre gapped" but to make sure, try to find some feeling gauges and drop them to about .028 cause I think they come .032 out of the package.

Usually for pump gas 11.0 is the middle ground for afrs. Anything below 10.5 is too much fuel imo so you're just wasting it and making the oil dirty in the process.

You can turn that bi*** up after you get some fuel goodies and tuning software LOL no sense blowing up anything when it's still running.

Sounds good LOL I was just wondering really. I mean 62 is almost fp black turbine range.

But yea also with the tb gaskets. Definitely get oem in there and only dab tiny bits of rtv around the edge just to ensure proper sealing. Some run 100% rtv but that is messy and not as good as a real gasket.

I was having similar problems with my audi I had. At a certain rpm it would face plant and this was all after I put new spark plugs in but didn't have a chance to gap them as I was hunting a cel down from a miss fire and I also needed to get a dsm part down the road at the time. After getting the part and getting home, I gapped them all to .025 and didn't have a studder again
 
Also for the tb to turbo thing, I don't believe the throttle body will be doing any type of restrictions on your turbo. I can't find anything to say the throttle body puts any back pressure on the turbo. I was running a 60mm 1g turbo tb on a fp black at 40psi and the throttle body wasn't a limiting factor. I also have a full 3" exhaust turbo back with no cat so the exhaust is pushed out very fast and easy.
 
I think I'd still like to find a 60mm tb, I've been told a handful of times that my BBK will leak first at lower psi on average than a stock 60mm from 1g or n/a 2g. And I'm pretty sure my dad has some feeler gauges laying around from his mechanicing days that I can borrow. Who knows, might have a plug out of whack. I'm a little curious though, because my plugs are a little white like they're burning lean, not black at all. Well, I'll half-way take that back, I've been pulling the same one. Maybe I'll see a difference in the others & find a coil problem. I'm patiently waiting for my income tax to arrive so I can finally buy a cable and software. Had some saved, then found a great deal on a parts car LOL my garage is packed full of 97 GSX parts now, everything but the frame, seats, carpet and I'd have the whole car if the trailer didn't junk out. After landing some tuning software I hope things come together a little easier, feel like I'm guessing half of the time and doing excessive maintenance the other half. Still love the car though, keeps me on my toes.
 
I've not heard much about bbk so can't tell you yes or no on that. A 60mm will be good tho. I upgraded to a 70mm s90 just cause I went sheet metal intake manifold and the oem throttle body didn't look as good hooked up LOL

That is always a possibility. I deal with 1g parts but tons of people on here have extra coil packs or such if that does result in the problem. Easy to check for spark tho. Probably easiest to look the process up on here just so you don't end up leaving the fuel pump fuse plugged in.

I hear you there man. Spare parts are always helpful regardless if you need them or not, cause you will eventually
 
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