DanD

Some will remember my previous post about using an NA block in my 86 turbo.

https://rennlist.com/forums/showthre...light=cylinder

Here's the latest update. I'm using an 87 924s short block. I changed the rod bearings, (they were fine, but I had it apart), change seals and gaskets, added a rebuilt turbo head, surfaced, belts and rollers and all that rot...
I was going to put in an extra thick head gasket to reduce the compression back down to stock turbo levels. But it was actually so thick (.125 vs .045 stock) that I couldn't use the alignment dowles to center the head. So I took that oppourtunity to order another head gasket, .065 this time. I really wanted to see how the engine would respond to the higher compression.

Note, my car has water injection and SMT6 piggyback computer to manage the induction charge. Here's a complete list for those wondering.
87 924s engine (same as 944 for those who are unaware)
Perfect Power SMT6 piggyback
Snow performance water/alcohol injection
T3/T4 #8 hotside .54 trim compressor
65# injectors
3 bar fuel regulator
Apexi Electronic boost controller
Stock wastegate (pretty much wasted...:^) 15psi max
lightened flywheel. Centerforce clutch.
"open" stock exhaust
LSD transaxle
fiberglass hood and GT header panel
track suspension and other safety items

Driving impressions.
I starte by putting about 5 gals of 100 octane gas in the empty gas tank. That allowed us to tune far and wide without melting the pistons. My son does most of the tuning, I just press the go pedal and have fun. He reads the LM1 Wideband and tweaks the laptop. We've tuned on it a bit and still have more to do. But overall, it's night and day from it's previous worn engine. It did have a K26 turbo before the NA swap.

It's basically a rocket in 1st and 2nd gear when the tires grip. We have two boost configurations on the Apexi. A is everything the wastegate will allow (15psi) and B is about 10psi. Even with it set to B there is no traction whatsoever in 1st gear. we're now running on a mix of 70/30 91/100 octane gas. My chart says that's about 94 octane.
http://members.rennlist.com/dan10101/octanechart.htm

We'll be adding a KnockSense knock sensor to monitor the engine better than my old ears can. Then we can try 91 octane and water injection to see how that fares. http://www.viatrack.ca/ (Thanks Claus for that tip)

Enough for now. Here are a couple pictures.

Rock

we used an 86 N/a blocken in my turbo. Runnin fine.

DanD

I knew there were a couple of you pioneers out there. What's your setup? Do you have any detonation to deal with?

Zero10

Yeah, but IIRC Rock, you used turbo pistons?

I was planning to do a similar swap, but by the time I figured in the cost of a big turbo, standalone management, a good condition block and all the work I decided that a V8 was cheaper and had no turbo lag. That will be going in once I get the cash

In regards to your project, it looks good. You can probably get away without water injection at 10psi on 91 octane. A knock sensor will tell you for sure though, and that is a wise choice. It would be interesting to see that on a dyno!

DanD

Thanks Zero.
I did use the factory 924s short block. 9.5 to 1 compression ratio or thereabouts.

I already had all the misc pieces, just a good short block. If I could have found #2 turbo pistons for a reasonable price I would have gone that way. But, this is a good test. If all goes well, I may even build a turbo motor with higher compression.

Zero10

You will be happy with the 9.5:1 CR. Everybody who has done it so far has commented on how much the low end torque is improved.
Sure it limits your boost and therefore peak HP, but you can still make 300+HP, and it's very streetable.
I wouldn't go above 10:1 if you are adding boost. I'm sure people have done it, but you wold have to either limit boost to 3-7psi or run race gas all the time.
Then again, I am by no means an expert, these are just my opinions.

I turned this very same idea over in my head for a couple months. It was very tempting.

aeronautica86

what would be the limit of boost one could reliably run on a daily basis, with pump gas with the higher CR?

DanD

I'm guessing it will be 10-12psi without water injection. Others have said 15psi. I'll let you know what I find.

Zero10

On 91 octane 10-12psi, on 94 you could probably push it to 15psi. 15psi with a proper tune should give you a solid 300hp. Perhaps even 300rwhp.

If you ran water/alcohol injection and race gas... you could probably hit 20-25psi. That would be something to see.

AL951

Congratulations Dan!
Sorry I didn't get back to you yesterday, as I was on Laguna Seca for the A1 grand pirx.(I will sent you a pm)

I am very happy that your project is going very well. maybe you can take me on ride one of this days.
How much Hp do you think the engine has as of now?


Regards,
AL

FSAEracer03

I have a stronger wastegate handy if you need one.

SchnellerUmsetzer

I was under the impression that the oil for the turbo came from a hose that connected to the block thereby NA blocks and Turbo blocks were different!

caster951

The oil for the turbo comes from a tapped hole in the upper balance shaft housing IIRC. Later blocks have this hole there, but capped off. So, a later NA block can be adapted for use to oil the turbo.

DanD

Here's a pict of the turbo oil connection on the NA engine.

I'm currently troubleshooting a cold running problem that has progressivly gotten worse since the install. Still looking for sloppy workmanship and so far not finding much. Well, I've found plenty, but nothing fixed the problem so far.

DanD

Sounds like fun Al. Looks like a great racing series.

As you know now, it's not going great, but when it runs right, it sure goes!
I'm guessing between 275 and 300 at the rear wheels. I was making 250 at the rear wheels (dyno) before the last round of mods. It feels a lot faster. I look forward to your project, It would benifit me to move to a stealth system. For piece of mind if nothing else.