Engine rebuild quandries.

[douglas vincent]

Repeat after me.

Always include engine management when pushing over 6 psi.
Always include engine management when pushing over 6 psi.
Always include engine management when pushing over 6 psi.
Always include engine management when pushing over 6 psi.
Always include engine management when pushing over 6 psi.


I broke a ringland or two I suspect, on two separate occasions. First was last week when attempting the blower AND a 60 shot of nitrous (did get a 14.7 et, if I had a clutch it would have been a 14.2). Then tonight I took it out again to the dragstrip and on the last run I heard metal bits seemingly moving through the exahaust with lots of tailpipe smoke. But.....wagon still runs pretty swell with only about a 10-15% lost of power overall. However I am suffering a large amount of blowby due to the damaged piston. While on the freeway, cruising in fifth has weird hesitation/missing most likely due to the wacko ringland damage, but as soon as it gets a little load going, then the missing disappears

I still have to compete in next weeks rallycross, so cross your fingers.


So now comes the question of the rebuild.

First fact is I need some kind of ignition timing control, whatever shape or brand it takes. This could be anything from a DIS-2, to a Perfect Power.

Next is the question of pistons. Turbo pistons are the same price as stock NA pistons. But what are the pros and cons of turbo versus stock NA?

Compression baby.

I suspect if I were to go to turbo pistons and stay at the same boost I currently am running, I will actually lose power. Right now on the NA compression I am hitting almost 160 whp. Turbo legacies running the same boost are maybe making 180 crank power versus my 210 chp. So if I switch to turbo pistons, I lose ALOT of power. But I can up the boost though now because of the lower compression, but I am limited to maybe pushing 12 psi if I were to spend another $350 on another custom crank pulley which would net me about 180ish whp.

Now thats all fine and dandy, but it involves running higher boost with the extra cost of the new crank pulley. However, this lower compression may NOT need the timing management.

Or I can just rebuild like I did the first time, with regular NA pistons and run 9.5-1 compression. BUT with engine management so I can knock down that pesky detonation due to advanced timing. Running higher octane than pump gas is not out of the question, I already do it. Currently I am pushing 8 psi, and with some modification to the intake, I probably can get it up to 9 psi at 3500 rpm, rising to about 11 at 6000 rpm. And this is without messing with the current crank pulley. If the engine management works at keeping the detonation at bay, then I should be getting close to 190 whp with AMAZING torque.

Thats the internal question to the engine rebuild.

Next is the question of WHICH engine to rebuild.

I have the "broken" engine in the wagon currently. It runs and drives fine and dandy minus the few hiccups it is having. If I rebuild that motor, then I will be down about a week if I choose to have the current heads rebuilt. If I have a set of new heads ready, then I have to rebuild during the pull and this would add about 2-3 hours to yank the heads and pull and replace the pistons. Unless the piston sleeve(s) is damaged, then I am confident in the bottom end of this block.

The other option is rebuilding a donor block I have sitting. Now theoretically this NA block should give me the same performance as my current block. It was running fine when I pulled it out of a donor wagon. But I think giving myself the extra three hours of involved install work on a proven block is the better way to go.


So really the only question is this; Turbo versus NA pistons combined with a static 11ish psi of boost. Which is going to give more power when combined with decent octane fuel AND ignition management (and possible fuel managment).

[dzx]

You could pick up a greddy e-manage and an ignition timing wiring harness for it or you could pick up an apex'i ITC like i have. The greddy e-manage is fairly inexpensive and so is the ITC however the ITC is a little difficult to locate.

[BAC5.2]

Where are you buying the turbo pistons?

Remember, the efficiency of your supercharger isn't the same as our turbos.

At the same boost, you make more power, but boost isn't the only thing that determines power.

I made 100lb-ft more than DZX did on the same boost with different turbo's (and he has mods that I don't yet have).