Guys,
I have never played with turbos, except on diesels, What would be the lowest comp ratio that it would be adviseable to start with and would a lower comp ratio (5 or 6 to 1 or) with more boost make more power? As it does with a roots type blower. Also would there be an advantage to multiple small turbos over one or two larger ones.
Pros, Cons, opinions?

Just idle thoughts on a sub zero morning.

Maybe this should be in a different section of the B board like performance or bench racing but I wanted everybodies thoughts.

Whats the intended use of the engine or are you just asking?


More boost ~ less compression


One or two turbos? Get ready for opinions.

i,d say start with atleast 8 to 1 comp. any lower and the engine will be a turd. higher than 9.5 and you will be boost limited by fuel very quickly. i presently have my engine around 8.25 and have run the boost safely to 12 with 91 octane. also using a intercooler. i also run 1 turbo. it simplifies the install. some will say 2 turbos spool faster, but i have found that if set up correct 1 turbo spools plenty fast. especially on our relatively small cube motors. tom

Inline 300

Just me thinking. I am building a roadster for a gentleman with a 2000cc four in it and we were talking about what could be done to make it eat medium V8s. That got me to thinking and you know where that will take a person. I got to thinking about small turbos like for motorcycles and then started to wonder if special pistons were made to lower compression ratio and a large cooler was installed, what could a person come up with. I was thinking small turbos would spool up faster to help off set the power loss at low rpms due to lower comp.ratio. Don't know if any of this would work or not so am asking for opinons or experence if anyone has ever tried it.

First off, you do not want to use a turbo sized for a motorcycle, too small.

Now a days ,turbos can spool almost as fast as you want to.
Selecting the correct turbine housing, ball bearing center sections all affect turbo spool up time.

Reason factory cars run about 8.25- 8.5 to 1 compression is because it is made for the general public. The intercoolers are all too small, turbine housings ,too small, all add up to higher intake temps. which in turn you need to keep your boost lower.
My Syclone pick up truck ran 14 lbs of boost pressure stock. 8.3 to 1 approx.
I now can run 22-24 psi boost pressure w/the help of methanol injection. Aquamist 1S system.

Best thing you can add (Methanol injection) to your turbo application to supress detonation & up the boost period!

People are leaning towards 9 to 1 compression lately.
If you get the correct combination you can run 8.5 to 9.0 to 1 compression & run anywhere from 12 - 26 lbs of boost pressure on 91-93 octane gas
w/added methanol injection, no problem.

MBHD

MBHD
I was thinking on the 2000cc engine that twin small turbos would work, don't know. I know on our chy.hemi we ran 5 to 1 with 30 lbs boost when we hit the traps, but we used a teflon sealed roots type blower. This allowed much more power than when we had 8.5 to 1 CR. I don't know if a turbo will respond in the same manner or not. I am thinking of a large cooler. I would like to run this engine on prem fuel but no Methanol. I want this vehicle to be user friendly and I can see it running out of methanol and trashing itself. These are things you have to consider when you build for other people. By the way it has a 5 speed so it isn't limited by a stall speed.

cool big bill, sounds like a cool project.


as far as, single or dual turbos, ideally, you go with a turbo thats application speicific, then it will do what you want it to do, it takes a little to understand turbo sizing or it did for me.


a good internet source to learn about turbos would be I believe "turbomustangs.com", look in the knowledge base, alotta information, it began as a mustang site but they have other make sections, shouldnt be hard to find something on a turbo 2.3. there are a few good books out there as well. Is this a ford 2.3 your talking about? They can be impressive under boost.

you want a load on the engine to spool up the turbos.

I wanna see pix of this roadster build up.


good luck

As far as I can tell the jury is still out on twin turbo's vs a single turbo, I think one properly sized turbo might be best, it's less money, less plumbing, less weight ect..

Most high perf VW(air cooled)engines are around 2000cc and there are alot of turbo kits avaliable for them. Just a thought...

Dan