'90gsx rebuild, need opinions

[mrjreezy]

Hey guys, I am now the proud owner of a 90gsx that is not running. Picked it up for $1000. The previous owner says that it has a bad oil ring. There's oil in the #3 chamber so this is probably true. Along with the gsx I received a new block and crank. The block has been honed, aligned, and bored. The crank has been polished. (I have the receipt and picked it up from the machine shop myself).

I recently bought wiseco deep dish forged pistons and Manley H rods. I plan on using the stock heads of they're still in good shape. As of now I'm leaning towards ffwd dks 272/272 cams. I'm also upgrading valve springs and an oil pump.

As far as Turbo goes I'm thinking a 16g. Maybe a hx35. And of course dsmlink for tuning


The gsx is being built for Autocross and will be an occasional weekend driver. I'm looking for around 400-450whp. Any opinions or advice you have about this setup will be appreciated. I'm not looking to be cheap but I'm not looking to spend a fortune either. If you have anything to say then please do. Thanks in advance.

 

[My1GLaser]

If you want 400-450 then go for the HX-35. Get the 7 blade so there is room for upgrading down the road. I ran mine in the DSM bolton housing for a little over a year getting about 47-48 lb/min airflow. I just switched to a T3 setup and turned up the boost and am getting about 53 lb/min now. Thats on a 2G TB elbow and stock IM. I am switching to SMIM & NT TB with 2.5" silicone elbow and am hoping to pick up a couple more lb/min.

The 16g would spool about 5-600 rpms sooner which will be better for autoX, but you won't reach 400-450 without an insane build. It can be done, but only by a few...

I love my HX-35. I get 35 psi by 4K in 3rd. It spools very quickly, but I run 60% E-85 and that helps with spool.

With some timing advance in the spool-up range and adj cam gears to retard the exh cam some, you can get it to spool quicker than normal on pump gas.

 

[mrjreezy]

Yea I was thinking the hx35 would help me reach my HP goals. Didn't know how well it would work for me doing autoX though. I think I'm going to go with the hx35 and get adjustable timing gears like you said. Still weighing the options though.

Would it be better to lower how much power I want and just get a Turbo that spools faster. I'm going to be a newbie at autoX and just want to know what would be better for that.

 

[cyclonekid77]

My car made 461awhp, and my intentions were to build it for autocross. Take it from me, that much power is WAY overkill for an auto-x car. If you want to autocross these cars, put a 14b or 16g on it so you have response in the lower rpm range. Any turbo capable of 450whp will spool way too late to be useful on an autocross track. Trust me, been there done that. I have 10 times more fun auto crossing my 100whp miata than I ever did in the dsm.

Buy good tires, quality suspension bits, and a small responsive turbo and you will have fun auto crossing your dsm

 

[My1GLaser]

Keep in mind that the your upgrades will put you in different classes. And stiffer competition makes it a lot tougher as a novice.

I would look into the classes and allowable mods and plan your build. I autoX some, but my car is so modded that I am in SM class competing with very skilled drivers and much better performing autoX cars.

After the rear toe eliminators and solid rear subframe bushings I installed before the last race, I was finally ahead of the average Subies by a couple seconds. I was still several seconds off the SM leaders, but still happy with my times.

Suspension, weight reduction & tires!

And ^ he has fun because its a Miata! They dominate the autoX