WOTTECH wrote:Rettax3 wrote:So far as the tiny TB, I wouldn't worry that much. It is a major power-limiter as it restricts the flow on the stock setup, but with forced induction, breathing is totally different on the engine's intake side. Look at it this way: what is smaller, the TB at wide open, or the outlet from your turbo's compressor? BTW, if your turbo actually
has a larger opening, you
seriously need a smaller snail!
It is like the 3400/3.1 hybrid in my '90 turbo 'Retta. I have a fairly aggressively ported set of heads and intake from a 3.1 MPFI turbo LG5 sitting on top of a stock low-mileage 3400.
Superdave and others laughed at the setup because the MPFI parts breath so badly compared to the 3X00 engines that even with porting them out the best you can get are flow rates similar to a stock 3400. But, with the turbo pushing air through the intake system at higher pressures and higher velocities, intake flow is no longer the restrictor for power -engine internals and tune are probably the limiting factors on my build, and with stock 3400 injectors on my car I am close to the maximum fuel-flow they can deliver... Plus, higher velocities mean more turbulence in the combustion-chambers which equals more efficiency and increased power, even at less-than-peak RPMs, so optimum intake flow may not mean maximum intake flow... Personally, I would rather have a car with a lot of character that can demolish a stock version of itself than a faster car that anybody can buy. I like your build concept, and applaud your determination on it. I still just feel that your turbo is too big for how you plan on driving your car, and I think you would be a lot happier with a smaller turbo.
How does restricting airflow increase efficiency in a boosted engine? I am at a loss for what you are stating as facts.
I wouldn't use a 2.2 so I can't really help with the thread. I just skimmed cause I saw 3.1:P
Sorry if I was unclear, -in my experiences with motorcycle engines (small engines pushing over 2 HP per cubic inch, normally aspirated -that would be like a 3100 making over 300 HP off the showroom floor), efficiency is everything, and very small changes can result in huge power differences. Smaller carburetors, smaller intake tracts, even restrictive intakes can yield more power at lower RPMs than huge gaping maws -how? It
is a fact that combustion-chamber turbulence is, to a point, proportionate to intake velocities. It
is further a fact that increased turbulence will also increase flame propagation speed inside the combustion chamber, which increases power and efficiency. But... I did
not mean that restrictive intakes in any way increase the power potential of any given engine -just that it might increase its' power at some specific RPMs, somewhere far below peak HP. I also did NOT mean that intake airflow wouldn't limit some engines' power -just not mine or
Koots's as we have other limiting factors that we will encounter first. I meant that the tiny 2.2 TB would not be the limiting factor for a turbo-charged build on
Koots's engine (I believe we've both stated that pretty clearly). I was just trying to point-out a silver lining in the cloud of limitations...
I don't believe that whether or not an engine is boosted would matter to the necessity for turbulence inside the combustion-chamber.
Some of my supposition stated earlier was based on my experience with my 3400/3.1 hybrid mentioned above -the intake runners and upper plenum are so restrictive that the TB's size is not a major limiting factor, and I am assuming that the 2.2 is engineered in a similar way, as it was not built as an RPM engine, like the 2.3 Quad was. Now, putting a 3.1 MPFI TB (or
Koots's 2.2 TB) onto a 3400, N/A or boosted, would certainly restrict the intake to the point where power would be lost in most or all mid-range and higher RPM bands, but such an extreme is also not what I was talking about. Likewise, putting a 90mm VH45DE's TB onto the same 3400 won't help it much
anywhere, except for
maybe peak RPMs, and will likely hurt performance or efficiency in low RPM bands, particularly considering the severe mis-match between TB size and intake inlet diameter.
Going back to the motorcycle engines, which reveal changes so dramatically that they can actually be noticed as evidence, I have an old Kawasaki Z-1, and it was modified with
smaller-bore Mikuni carburetors than the stock TBs, and the low-end torque and throttle-response is significantly increased from stock, so much so that I've actually managed to break a drive-chain on it once (this particular bike is down for a turbo-charging and re-styling project, to be finished once I've got a death-wish). Again, this is real-world, this is fact. It also may not translate as well to other engines as I believe it does, so I stand on what I've said, with the acknowledgement that I may not have said it clearly, and that I may actually be wrong about some of it -it wouldn't be the first time. Cheers.