tuna55 wrote:
Well, let's focus on application. What diesel trucks etc can I get that from? I am OK with twins if necessary, but I'll need to know how big. How big is too big? What happens from too big? If too big actually equally more performance but with more lag, I can fix lag with a little nitrous at the starting line, or something like that. I've often heard of retarding the timing to the max to get the turbo spooling while on the two step... so, without going to small, assuming a 350 cubic inch engine at 6000-6500, how big is too big for singles or twins? Where can I get them?
Also, I have no idea what "depending on the hotside" means, other than maybe the size of the exhaust side of the turbo, but I didn't know they could vary...
Thanks
-Brian
A lot of people mix and match turbo parts. You can use a turbine off one and a compressor off another to build a hybrid turbo. Smaller turbines spool faster with less lag, but restrict the top end and will over rev causing self destruction. Larger turbines have more lag, but less top end limiting. You need to match the compressor to the engine. It needs to put out enough air to maintain boost through the rpm range. A small compressor won't move enough air to keep the engine fed, and a large compressor will move so much air the bov or waste gate will dump, wasting all the energy used to spin the turbo. The compressor also is dependent on turbine side since that is what determines how fast the compressor turns.
Most turbos have a sheet showing how much exhaust volume needed to move so much air at a given boost pressure.
The other option is to find a turbo off a similar displacement engine and go from there. With a diesel turbo I would probably go with a larger displacement given that most diesels turn about half as fast as a gas engine. That is just a guess though and I have no information or facts to back that up. Then again, diesels run massive amounts of boost...up to 50lbs which changes the size needed to make less boost for the same displacement.
Lots of variables and with a guess all you can do is trial and error.
With the cost of diesel turbos and the cheapness of turbos on ebay, if I were in your shoes I would go with two turbos sized for 4cyl engines and twin turbocharge it. It would probably cost less than one big diesel turbo.
+ slicks + suspension + chassis certification... it'll add up quickly.
