Alright guys, I just removed and tore down my motor. It's a 1987 GXL that I'm looking to throw some boost into it. Probably somewhere around 10-15psi or so daily and no more than 20psi for the power tune. I hear that you want to run low compression rotors for running boost so I'm looking for information about why and what rotors would work best. The rotors I have now are 9.4.1 and wasn't sure if I could run them or what the complication are if I do. I'm also having it bridge ported if that makes a difference. Looking for everything really. Which ECU, size injectors, what rotors, what seals, etc. anything to help me get a little more information on what to run and why.

I'm looking to get 350-400 to the wheels without going over 20psi. Not trying to be the fastest on the streets, just something I can have fun in and slide it around.

Any information helps. Thanks

 

First step should be a wander through the FAQs. Pay particular attention to the "turbo NA" section and the links within.

Next, the Archives to read up on some common issues.

After that, head over to the Single Turbo subforum for some reading on turbo sizing.

That should lay down a foundation.

To get you started, you're looking at a turbo like the GR35R which will put down about 400HP on that NA engine around 16 PSI.

Your ECU choice will depend on what you have prior experience with and what your tuner knows. The Haltech is a good choice, if you are into DIY then the MegaSquirt is also widely supported on the rotary. Stay away from the stone-aged Microtech.

Once you've done some reading, come back and I'm sure we can answer your questions.

 

bridging the 6 port irons is a waste of time(there isn't much to be gained beyond the stock secondary porting, primaries can be opened but but bridging solely the primaries results in poorer drivability for virtually no power benefit)

using the 6 port irons on a turbo engine is a waste of time(they flow like *** with a modified turbo intake and using the 6 port intake and fitting the turbo is a difficult task. the intake actually outflows the exhaust porting and will begin to stall the compressor at higher revs unless it is a larger framed turbo and specifically NOT a hybrid stock turbo. this was tested on a 6 port 9.4:1 engine on both a stock rebuilt turbo and a stage 3 hybrid with the wastegate held completely shut, beyond 6500 the boost just fell off no matter what)

wanting to go over 14psi on pump gas with 9.4:1 rotors is a waste of time(compression will limit boost due to increased detonation at lower boost levels)

wanting to push 20 psi on pump gas even with the proper turbo rotors/irons is a waste of time(beyond 18psi premium pump gas is going to be very unstable due to the combustion temps at that boost level, you can supplement it with water injection however)


in fact building the whole n/a car up to handle 400+whp is a waste of time. sell the GXL and buy someone else's turbo project, or keep the GXL as your daily and buy someone else's turbo project.

 

I have no intentions in selling the GXL. But I have been contemplating buying 89-91 housings, plates and rotors. Any experiences with which plates, ports, rotors, injectors, anything that would be the best for boosting.

Aaron cake I'll swing over to those pages and relearn my reading skills lol.

 

Okay so after reading a lot of the single turbo forum there was a good thread on compression rotors. What I got from it other than people debating which is best, is that the higher compression rotors such as the 9.4 can run equal powers to lower compression rotors 8.5 with a lower amount of boost.

Problems I've hear was something about timing. about how much you have to advance and retard your timing. Which I have no knowledge about.

I would be all for running lower psi if it means I can retain my 9.4 rotors. 10 psi or so I'm not looking for this to be a street monster.

 

the lower compression S4 turbo rotors make bigger power more reliably but with a narrower power band(aka dyno queens). S5/FD 9.0:1 rotors have the best all around response and power, the higher you go the less boost you can run safely so the power numbers shift to responsiveness.

there's no power gains in the rotor housings from S4 to S6 but the chrome on the later housings lasts longer and takes more abuse.

the S4 to S5 irons are nearly identical with the exception of the late series 5 turbo rear iron which can be thick casting and handle more power more reliably.

you can run less boost and make your power goals but it requires a bigger turbo, and with bigger turbos comes the treadmill of finding the perfect turbo/exhaust design with the best response for your target boost level.

in my experience the higher compression engines wanted more advance to make more power in larger amounts than the lower compression engines, but with more advance comes higher risk of going too far and running into detonation. it's much easier to get caught up in making more power with the risky high compression engines, you simply have to know when good enough is good enough.

 

So you would recommend 8.5 or 9.0 rotors if I were to boost it? I'm all for option. I've heard to only go one model apart if switching rotors, would that also need a new eccentric shaft balance weight? Or could I keep the one I currently have?

What would be the recommended for housings and plates. I'm looking to Bridgeport no matter what. You were talking about the 6 port plates. The 4 port a lot better then?

 

I just found the page that you turbo'd your NA. 13B. Great write up, and a great conclusion that I'm not going through all that to boost mine. Lol I'll go buy a T2 engine from j-spec auto once my car's all done at the body shop.

Thanks for clarifying some things up for me though guys. All is appreciated.

 

Yay..another JDM engine purchase.

Look into that will ya..They are not always a "good thing".
They have a saying. "you can shine up a turd..but it will still be ****".

 

What's so bad about buying an S5 TurboII engine?

 

its 30 years old, and been through a few hurricanes and a tsunami. IMO, buying a JDM engine is fine, but its so old you should open it up and at at least reseal it.

 

i heard lately they were also radioactive.

 

I would defiantly break it open and see what I'm working with. After all, they don't come with warranties... But that's when I would buy a new rebuild kit, port it, clean it. See what I'm working with and then go from there. They say they all pass compression tests, so at least I'd know it has chewed up an apex seal and eagle clawed the rotor housings. Or seized from sitting around.

As of now I'm fixing the body, repainting it and getting the shell 100% so I'm far from getting to the motor. Just wanted to figure out what's everyone's opinion is on what I should do so I know what I'm dealing with. My motors in good shape just dirty and am taking it to a hot tank tomorrow. After that I guess I'll look into selling some things.

 

JDM engine importers offer no warranty, no compression testing, and no information about its origin. You could spend $1600 on an engine and it could run and be fine. You could also spend $1600 on a pile of scrap metal. They don't even do basic checks. Banzai purchased an engine for a customer from one of these importers a few months ago and it was complete scrap and they offered nothing to remedy the issue. The company kept deleting my Facebook posts advising people not to buy rotary from them. Personally, I'd rather buy a used engine and rebuild it. At least then, you know what you have.