Twin turbo LL2 buildup

[2.8-350TBI]

Hey guys, I am new here, and want to start my own buildup
Today in class I got two free turbos from the prof. They are IHI RHF 4 turbos. I have an LL2 (2.8 TBI) in my 89 blazer 5-speed. I already put on a 350 throttle body and would like this to remain a budget buildup for now. I plan on running 5-8 psi on E-85 fuel until I get upgraded internals and MPFI going on. So, my question is, besides plumbing and oil lines, which i´ll do myself, what do I need to do/should I do to get my engine to run happy with the turbos?

[kflo 93 gt]

You're gonna need a good tune and probably a lot more fuel than the tbi can provide for 8psi. The last bit is just my speculation though, I'd upgrade the injection before trying to go twin turbo.

[no_doz]

hypereutectic pistons, wot-tech.com or summitracing.com is good for those, arp connecting rod bolts, stiffer valve springs. other than that 5-8psi shouldnt be a problem with a good TUNE (emphasis on the tune).

[Joseph Upson]

You really shouldn't need to do anything more than the best tune you can manage for it to run fine in stock form. 7-8 psi is not much at all for a stock 60 degree motor although the valve spring upgrade would be a good idea if you intend to rev it fairly high. Tunercat should have the tuning software available for it pretty cheap leaving you with the task of rounding up the hardware.

Many here have a lot more experience with this than what you may have at the moment so I feel it would be better for you to work with what you have until your knowledge base increases to avoid damage to expensive parts should you make a mistake, then later once you have a firm grasp of the do's and don'ts you can start a high perf bill.

I twin turbocharged my first engine around 1995 with a freshly built TPI 305 and fried the rings on the first run because I took a chance and ran it without a wastegate signal. When the power hit I couldn't get out of it I was so impressed. Nearly blew the head gasket to. It still ran fine except I had to disconnect the PCV hoses from the intake to stop the smoking from the tailpipe.

Pick up the book Maximum Boost also.

[SofaKingWeToddDid]

why go with twin turbos if youre only going with 8 psi? i know its going to look cooler, but it just invites more problems as well. and i dont know for sure, but ill bet my lunch money that if you had those two turbos going with anything more than 10 psi, its gonna make very bad things happen in the motor. (i could be wrong, but you have to come here for the money)

[geoffinbc]

The first thing wrong with this situation is the TBI system. Because there is fuel in the throttle body you can't boost it without fuel spewing out of the throttle shaft. So in order to overcome that you going to have to build a box for it like you would for a blow through carb application.

For E-85 your looking a lot more expense. First the steel tank and fuel lines have to go along with all the O-rings. The whole injector pod will have to go also since it is aluminum. Basically you wont find a stainless steel TBI fuel injector pod so you would have to update to and SFI flex fuel system at the least. So your most likely going to stick with gasoline and run a good intercooler and maybe a meth injection system if it needs it but I doubt it will under 10PSI of boost.

Your in luck with injectors though since you can choose from a host of sizes from stock 2.8L injectors all the way up to 7.4L injectors from the chevy big block.

Tuning is not so bad you just have to get a company like tbichips.com to work with you on a good chip.

[2.8-350TBI]

Thanks for the input guys, im going twin turbo for simpler plumbing and space issues, and also for future upgrades, im just planning to install ugraded rings, valves, and springs for the engine to be happy with a little boost. I WILL keep the tune top notch though. Does anyone have tunercats contact info?

Keep in mind, its not a weekend warrior project, but a fun(ner) daily driver.

Will the stock rotating assembly handle 8 psi?¿

[Superdave]

a small single turbo is more than enough for a TBI 2.8

[no_doz]

going twin turbo isnt going to save you any effort, i assure you. & if you really want TT then you need to get a 3x00 topend because the 2.8 ironhead topend doesnt breathe for shit.

[robertisaar]

going twin turbo isnt going to save you any effort, i assure you. & if you really want TT then you need to get a 3x00 topend because the 2.8 ironhead topend doesnt breathe for shit.

X2 for no_doz

[Joseph Upson]

I doubt he'll have fuel comming out of the throttle shaft, if it has that much play then it would also be subject to a vacuum leak. I'd expect it to seal just as well as an FI throttle body. Since the injectors sit above the throttle plate and spray fuel above it there shouldn't be a problem. Turbo kits were offered for the Fiero four cylinder TBI engine not long after it went into production and they didn't have a problem along those lines that I was aware of. There is a metal hat like inclosure that came on some of the GM four cylinder TBI units that can probably be adapted in this case.

Note that there is a regulator present in the TBI unit so it will sense boost if I recall correctly. Whether it will do so at a 1:1 ratio I don't know. He will likely have to switch to the high pressure fuel pump which in the beginning at least the TBI engines did not have.

There was an electric carb that came on some of the 85ish and possibly later engines which would be more difficult to accomodate but the actual injected TBI units should work well as long as the fuel can be delivered against the boost pressure.

As far as integrity, I'd expect an 89 V6 to be at least as strong or stronger than the earlier engines that lived behind at least 7 or more psi on a daily basis but with a good tune.

Single turbos where practical are best in my oppinion. Reliability is key, more turbos = more plumbing and potentially more trouble.

[2.8-350TBI]

Thanks again, guys ill get myself some 3x00 heads before I strap turbos to my lil engine.
I also a detroit diesel 4-53 supercharger at my disposal. Maybe itll be easier?

[robertisaar]

Thanks again, guys ill get myself some 3x00 heads before I strap turbos to my lil engine.
I also a detroit diesel 4-53 supercharger at my disposal. Maybe itll be easier?

having worked on a few S/C DD motors before, i would just stick with the turbo(s) due to all the fab necessary to mount a SC on a manifold and keep it aligned...

[2.8-350TBI]

I have access to the machine shop at the college and plenty of aluminum. Either way, I'm making the intake manifold, and if I TC, the exhaust maniflods.suggestions?

[IsaacHayes]

3100 heads will need the 3100 intake manifolds and throttle body. 3100 intakes are multiport injection, not TBI... Just FYI.