Turbo motor compression.

How high is too high?

I know that high compression motors are not good for turbo charging. As general rule what is the highest compression you run in a turbo motor?

No general answer to that question. So much depends on tuning, bore size, combustion chamber shape, etc. I like the theory behind still having high-ish compression ratios with a turbo- so you still keep some bottom end and hopefully can spool the turbo up to boogey speed quicker.

My current car is a relatively small bore and high compression. Swift GT, factory 10 to 1 compression with 10 lbs of boost. I have no detonation, and probably 40k miles on the setup with no engine issues (tranny is a different case :) ) Once the standalone goes in, I'm hoping to get it up around 15-18 lbs.

There was an earlier post on here with a civic with a D16 turbo'd.... pretty good writeup. I will try to find it......

I would honestly look into fuel/timing on ur 4.9 Trans_Maro, that seems like a very boost happy CR.

Just a wag, but I would check it, that or goto a lower heat range plug.

My Pontiac 4.9 litre has 7.5:1 and a small turbo and I still find it laggy.

I'm thinking about running flattops and bringing the compression up to 8.5 but I get detonation at 12lbs boost rigt now.

Shawn

I have heard the E85 is a pretty good fuel for turbo'd engines, just hard to find. Truth?

Look for my build post. I'm running 10 psi on top of 11:1 compression. I like it.

DILYSI Dave wrote: Look for my build post. I'm running 10 psi on top of 11:1 compression. I like it.

So, turbo on the stock 9.6:1 of a D16Y8 should be okay?

I may be out your way next weekend. If you're going to be around and don't mind visitors nosing around your car shoot me a PM with your contact info.

As long as you fuel it right and keep the boost in check I think you'll be fine. I'm running E85, which is 105 Octane.

For a stock D16Y8, I'd keep it under 6 psi and run 93 Octane. Still should wake that motor up nicely.

In general, visitors are welcome. Next weekend is no good though. Sorry.

cwh wrote: I have heard the E85 is a pretty good fuel for turbo'd engines, just hard to find. Truth?

Truth. E85 is very high octane relative to pump gas, so you can crank the boost/timing/compression without as much risk of detonation, and more than make up for the power loss you'd elsewise take from going to the lower-energy fuel.

However, I'd be reluctant to build a motor around E85, as it seems to be common in the midwest and nowhere else. I've never even seen it out here in California.

What kind of power can I expect out of a D16Y8 with 6 pounds of boost? I've found a complete 1998 Civic EX for cheap that would be used as a donor car for a 1989 Civic DX Hatch.

I've also considered a turbo powered B18. I think I could find an 89-93 LS Integra donor car for about the same price as the EX.

So, which motor would be best to use with a turbo set up in an EF Hatch? The D16 or the B18?

Did someone say E85? (Sorry for going off topic, I just happened to see this gas pump last week at at farmer's co-op in central MN.)

Stuart, how much was the E-85?

Around $2.05, if I remember correctly, I didn't look very close as I was filling up with regular. I'm not sure what the E20, E30 and E50 cost, but they ranged somewhere between the cost of E85 and regular, which was about $2.60.

Do the compression guidelines of Turbo also apply to Supercharged?

Dan

914Driver wrote: Do the compression guidelines of Turbo also apply to Supercharged? Dan

Yep. Engine doesn't care how it got boosted, just that it did.

ReverendDexter wrote:

cwh wrote: I have heard the E85 is a pretty good fuel for turbo'd engines, just hard to find. Truth?

Truth. E85 is very high octane relative to pump gas, so you can crank the boost/timing/compression without as much risk of detonation, and more than make up for the power loss you'd elsewise take from going to the lower-energy fuel. However, I'd be reluctant to build a motor around E85, as it seems to be common in the midwest and nowhere else. I've never even seen it out here in California.

Availability is definitely an issue. I wouldn't build an E85 Daily Driver unless I lived in corn country. For a race car like mine, I carry a 5 gallon jug with me wherever I go.

jwdmotorsports wrote: What kind of power can I expect out of a D16Y8 with 6 pounds of boost? I've found a complete 1998 Civic EX for cheap that would be used as a donor car for a 1989 Civic DX Hatch. I've also considered a turbo powered B18. I think I could find an 89-93 LS Integra donor car for about the same price as the EX. So, which motor would be best to use with a turbo set up in an EF Hatch? The D16 or the B18?

Power - 170 to the ground +/-. Anything much over that and the rods become a weak link. I had to rebuild mine due to bending all 4 rods. I'm at 202 HP / 185 ft-lbs.

The B18 loves boost. It's good for over 200 HP stock I think. If I was building a street car, I'd go with a B Series. Mine being a race car, the 100# I saved by going with the D-Series was well worth it.

Best depends on your goals and budget. There is no single right answer.

DILYSI Dave: This would be a challenge car build. So, it wouldn't see too much street use. The 100lb difference might make it worth it to go with the D16. I'm not looking for huge amounts of HP.

The D16Z6 we've got on our Howdy car is sitting at 9.5:1 with Vitara Pistons and stock rods, and can swallow 20 psi on 109 octane. With our baby Garrett turbo, we were going for broke on the drag strip at the '09 Challenge and took off our boost controller and wastegate signal line. The compressor's so inefficient at that pressure it's not even funny, but the engine could handle it.

As far as D16s for the Challenge, well, I'll be happy to tell you anything you want to know about our engine. We're very happy with how it turned out.

unevolved: do you guys have a build page somewhere for the howdy car?

Here's a short play-by-play of the buildup of the car:

http://grassrootsmotorsports.com/forum/grm/texas-am-howdy-civic-buildpictures/15215/page1/

But you've already seen that. Beyond that, I'm afraid I don't have any technical information published anywhere. But here's what I can remember off the top of my head:

D16Z6- came with car 75.5mm Vitara rebuild kit from FJD- $300ish DSM injectors- $50 on CL Garrett TB03 off a Volvo 740 (I think)- $9 (half-price junkyard days and inept clerks ftw.) Broken Greddy Type-S BOV- $20 on CL Semilog manifold- $60 on eBay (IIRC) Used Exedy Stage 1 Clutch- $50 from forums

That's the main things, we did the machine work (decked the block for the Vitaras) and ported the head ourselves. We tuned with Crome and wound up putting the used Ostrich ROM emulator we bought off CL in the car and budgeted, which we'll be taking out for next year to gain a little wiggle room to sort out some odds and ends.

Let me know if there's any other questions I can answer for you.

DILYSI Dave wrote:

914Driver wrote: Do the compression guidelines of Turbo also apply to Supercharged? Dan

Yep. Engine doesn't care how it got boosted, just that it did.

Mostly. Supercharged engines have less backpressure and can usually run a bit more timing - or withstand a higher compression ratio with all else being equal. Centrifugal superchargers tend to develop peak boost way beyond torque peak, so they're pretty engine-friendly.

Basically, lower compression will mean you'll make less power with all else being equal, but you'll be able to pack more boost in before you hit the Tuning Wall Of Detonation. On a turbo car, high compression means faster spoolup even if it costs ultimate power.

My GTX (7.8:1, I think) was a total dog off-boost. My 1.6 Miata (9.4:1) is a whole lot happier. Same basic engine in both, but the Miata has distributorless ignition.

So, this question was asked in another thread but I was confused on the answer.

Since this would be my first turbo build I might want to take it to by dyno tuned.

Do I have to count dyno tuning in the challenge budget?

jwdmotorsports wrote: DILYSI Dave: This would be a challenge car build. So, it wouldn't see too much street use. The 100lb difference might make it worth it to go with the D16. I'm not looking for huge amounts of HP.

Do you have a local source for real racing fuel? You can keep the compression high with that fuel, too. And fuel does not count toward budget.

OR....

Distill your own fuel.

(just don't drink it- not that safe)

E-

Personally if I had a choice I wouldn't bother using a D16Y8. The bottom ends have random dramatic main bearing failures. I've seen so many pop its sad.

If really wanting to do a sohc... it would be a vitara based D16Z6 or D16A6.

But... the B18 would honestly be the best choice. IF staying stock.

If building... people have managed 500+ on a D16z with vitara pistons and aftermarket rods.