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5yearplan · Post by **5yearplan** » Fri May 11, 2007 2:37 pm

So... anyone know of, or have a formula on the amount of "total compression"( i.e compression ratio, and boost) you can run, given an octane level before premature detonation becomes a problem, obviously heat and other factors come into play, but mathmatically.....

Greg Gordon · Post by **Greg Gordon** » Fri May 11, 2007 6:19 pm

The term you are looking for is "effective compression ratio" There are plenty of effective compression ratio calculators on the internet. Jim Stecks site has a great chart you can use.

5yearplan · Post by **5yearplan** » Fri May 11, 2007 6:51 pm

Ah yes, that phrase does sound familiar now that you mention it, I'll search google and see what I come up with. Would you happen to have a link to the page you mentioned off hand?

Greg Gordon · Post by **Greg Gordon** » Sat May 12, 2007 5:15 am

Sure thing, Jim Stecks excellent chart can be found here:

http://www.autocomponenti.com/boosted_t ... d_tech.htm

I am not going to claim to know a maximum possible amount you can get away with, and it will vary a lot anyway. The temperature of the boosted air entering the engine and the water/fuel ratio ore big factors not really accounted for here. If you plug in numbers from my car you can see that with 10 pounds of boost on a 9:1 engine and water injection I am running an effective compression ratio of about 11.7:1.

5yearplan · Post by **5yearplan** » Sat May 12, 2007 1:27 pm

Cool, Thanks.

GTV6GPTT · Post by **GTV6GPTT** » Mon Jan 21, 2008 6:07 am

http://www.youtube.com/profile_videos?user=mafiouso

some videos

Evert · Post by **Evert** » Sun Feb 03, 2008 11:03 am

Is it allowed to drop in with some boost questions about my 3.0 V6 12V bi-turbo project engine in this topic?

About air to air intercoolers. Is it wise to put electrical fans on them to cool the air while standing still or driving at low (city) speeds.

At the same time with an aftermarket ECU like the Emerald you can plot in several running modes with varies boost pressure. For example for my engine:

- low boost for city driving 0,3 bar (4,25 psi)
- middle boost for highway driving 0,5 bar (7,25 psi)
- top boost for circuit driving.

An how about cooling the bottom of the pistons:
http://www.autocomponenti.com/jets.htm
When is this necessary? The 164 an 916 GTV 2.0V6 12V are equipped with such a device. Is this possible to install this in the 3.0 V6 12V?

My 3.0 V6 12V engine has a CR of 1: 9,3 (with the 24V gaskets). When I read te diagram this is exactly 7 psi.
So with the air-to-air intercoolers (with electrical fans) top boost might go up to 10 psi?
Thanks in advance, Evert

Mats · Post by **Mats** » Sun Feb 03, 2008 12:24 pm

Evert wrote:
About air to air intercoolers. Is it wise to put electrical fans on them to cool the air while standing still or driving at low (city) speeds.

Thanks in advance, Evert

No, simply because at low speed or standstill you don't need any cooling capacity.

Rookie ROX · Post by **Rookie ROX** » Sun Feb 03, 2008 2:59 pm

Mats wrote: No, simply because at low speed or standstill you don't need any cooling capacity.

Agreed.

The intercooler is there to cool the charged hot air flowing through the turbo whilst you're on boost. During your low speed or standstill driving, you won't be on boost and only require cooling for the engine as per any other car. As soon as you start spooling and hit full boost (so say anywhere above 3000rpm) you'll already be going at a speed fast enough to induce sufficient cooling. Even if you were in a climate faced with high heat all the time, you still wouldn't use a fan. It's just unneccesary and useless weight.

As for running different boost levels - Most find it easy to simply have two settings, one lower setting for everday use, and then a higher setting for racing. Even then, if you're sensible with your right foot, you can easily get away with one boost setting all the time. It probably is worth considering water/meth injection as well, but I'll let Greg chime in on that, he explains it all better than I can! I'd link to his website but it appears to be offline at the moment.

ROCK ON
R~R

5yearplan · Post by **5yearplan** » Sun Feb 03, 2008 3:00 pm

what about fans to enhance airflow at cruising speeds?

Post by **Zamani** » Sun Feb 03, 2008 7:59 pm

Usually when on the move, it is unlikely that you would need a fan.

Duk · Post by **Duk** » Sun Feb 03, 2008 8:44 pm

Evert wrote:
About air to air intercoolers. Is it wise to put electrical fans on them to cool the air while standing still or driving at low (city) speeds.

Typically not required unless the intercooler is getting heat soaked from other hot components. WRX's suffer from this with their top mount intercoolers. I would say the Callaway GTV6's would have suffered aswell. Can also happen if the intercooler is squashed up next to the radiator in a front mount arrangement. Heat soaked intercoolers take the fun out of driving hard off the line.

Greg Gordon · Post by **Greg Gordon** » Mon Feb 04, 2008 7:05 am

I agree that with a properly designed front mounted intercooler a fan is not needed. After comming to a stop the intercooler will stay cool because it has a certain amount of mass and no boost flowing through to heat it up. The car will accelerate fast under boost so you will have plenty of airflow before the intercooler can heat up.

The only real advantage of a fan would be to cool the intercooler down between dyno runs. The shop fans usually don't do a good job.

Greg Gordon,
www.hiperformancestore.com

Evert · Post by **Evert** » Tue Feb 05, 2008 2:25 am

Everyone thanks for the clear replies.

Still there are some things not worked out by me:

1. How about cooling the bottom of the pistons:
http://www.autocomponenti.com/jets.htm
When is this necessary? The 164 an 916 GTV TB 2.0V6 12V are equipped with such a device.
Has someone already installed this in a 2.5 or 3.0 V6 12V?

2. My 3.0 V6 12V engine has a CR of 1: 9,3 (with the thicker 24V gaskets). I know that www.JS-Racing.net fits the turbo engines with special thick turbogaskets to lower the CR and to strenghten the gaskets. Is it not a must with all boosted engines?

BTW Very interesting site you have Greg...

Greg Gordon · Post by **Greg Gordon** » Tue Feb 05, 2008 8:59 am

Thanks Evert:

I don't think cooling the bottom of the piston is critical. With forced induction You can get enough power to break the transaxle without a lot of special work. I really don't think it's worth the trouble unless you are building some sort of endurance racer.

About 14 or 15psi is all you need with a 3.0 to have enough power to break parts behind the engine all the time. That boost level isn't that big a deal, lower compression forged pistons, and stronger rods are about all you really need.

Greg