I have an '88 GTU and I was wondering when it comes time to rebuild or replace then engine should I go all motor or try and convert it to turbo is all motor worth it?

 

What do you want, how much money do you have, and how much time do you have. The most you can get out of a reasonable NA motor is 190 or so RWHP, and that takes a lot of work. Without things like a stadalone and major porting, your looking at about 160 whp max. This will still be a fast car, but not breathtaking. Doing a turbo swap will yield much more power potential, but it will cost more money and a lot more time to do it.

 

you should get more than that for RWHP...i've heard of people getting over 200 to the wheels but you know could be a myth

 

Yes, you can get over 200hp to the wheels NA.

Is it worth it? NO.

 

200 is about the absolute max for a streetable port NA. That requires a good port, a standalone, and a good tune. In fact, I'm not sure if anyone's actually reached that yet. You can get 240-250 with a bridge, but you don't want to do that. Its not that streetable and doesn't last long enough to justify for a street car, at least not to most people.

 

Not to mention a generous helping of NOISE!

 

well as far as budget goes I am trying to plan that right now...my car right now is all messed up and is having extreme electrical issues and hesitation problems so I am getting it all rewired...I'm hoping that will solve at least some of my problems but after that I am looking foward to mods...I do however plan to upgrade my cooling system by replacing my thermostat and getting a koyo radiator...I was also looking into some type of cold air intake to remove the air box...

 

As an 88 GTU owner, I will say that they have all the desireable features you'd want an N/A without all the weight and ****. You've got the 4 piston brakes, LSD, and T2 suspension. It's a great nonturbo car. I think you should keep it n/a and get it running right with a rebuild. If you want more power later than just buy a turbo II

 

You're really not going to get more then 200HP without radical porting like a bridge. Bridgeports are just as reliable as streetports (or most other porting for that matter) provided that the person doing the porting doesn't cut the eyebrow into the path of any seals. The unreliability of bridgeports is a myth created by improper porting (the eyebrow catches the side seal and cracks it).

But to get that power out of a bridgeported engine NA, you will need a nice open and LOUD exhaust. For most people, the noise is unacceptable. Also keep in mind that a bridgeported NA engine doesn't have much down low, will idle at 1200-1500 RPM and buck during low speed driving.

Peripheral ports will make much more power, but will be even louder and have worse down-low characteristics.

What most people forget about when comparing to NA to turbo is the midrange torque difference. Any higher HP NA engine is going to be lacking the midrange that a turbo engine will easily produce. The torque curve of the turbo engine is vastly superior to the NA.

 

so would it be more feasable to bridgeport just the aux ports than to bridgeport the whole thing? (sorry -i dont mean to hijack)

 

Don't just Bridgeport the aux ports. I think I set a bad example when I did that...Mine is an experiment to see how it works out in a turbo application.

If you are going to bridge, don't wuss out. Either do a half bridge or a full bridge and you'll be happy. Of course this assumes you have the standalone to run it and the skills to tune it.

 

lol..i'm learning as i go. as for just bridging the aux ports - why did you feel that it's a bad example?

 

It has a lot less port timing then a half or full bridge so you are missing out on a lot of duration.

 

so a standard streetport won't really get me anywhere? what are the benefits of going to 3mm apex seals?

 

I have an '87 6 port NA motor I will sell you and you can take your time rebuild it and then when ever you get it where you want it do the swap. Just a little plug

 

Why did Kahren do (make 200 reliable, streetable horsepower) it with only a SAFC, mild port, and bolt ons?

 

because mild port? i think it was a kahren port he made himself. also it was other things. and i thnk it was in a 4 mort t2 in na form.

 

haha how much for it?

 

A streetport is worth it if you are rebuilding the engine but I would not take apart a perfectly good engine to port it unless you really want the port. Some will argue (those who don't know what they're talking about and should stop spreading misinformation) that a streetport on a 6 port NA is not going to result in a power increase. But those people don't have a clue and should stop making statements like that. A properly done port will result in a 20% or more power increase without effecting drivability...

3MM seals are pointless. Only use them if your rotors are too worn to accept 2MM seals.

 

It was a 6 port, streetported, custom intake manifold, SAFC2 and 4 x 550cc injectors hitting 85% pulsewidth. He said, because he was fuel limited, he only made 190 whp.

 

yeah Kahren has some badass manifolds

 

I was under the impression that Kahrens made something like 196. I forgot it just had an safc, but still, it had a custom manifold and a very good port job. I'm actually going to try for 200 once I get a megasquirt, but I'm realisticly shooting for the 180's.
Also, I've never heard anyone say a streetport won't result in a power increase, except maybe mazdatrix, who thinks its worth while if you happen to have the engine out and you want to blow some money (at least thats how it come accross.) My car has a street port, as well as ported exhaust, and there is a HUGE difference. You can't tell much differnce down low, but up high it is like a totally different engine. It develops good power well past the redline.