True or false?

from my experience higher compression doesnt quicken spool, but it makes more power vs same lower compression setup , and helps with off boost throttle response.

 

That sounds like that is correct!

 

Is pricing out yet?

 

Higher compression simply means higher cylinder pressure at a given point. Not necessarily quicker spool.

 

any updates on this?

 

Higher compression should spool a turbo quicker to some degree. Higher compression will give more exhaust energy to spool the turbo.

 

I finally got solid quotes on a the custom parts and there will be a 8-12 week lead time.

We are using some trick stuff and this will be a very bad *** motor.
One of the major factors affecting RPM limits are the rod bolts. They are stressed the most on the exhaust stroke when the piston is nearing TDC. The rod bolts have to keep the rod & cap together. We are taking our motor one step beyond and using some high grade hardware for the rods.

Most aftermarket rods use ARP 2000 material which is a good material. A step up is the L19 or H11 tool steels. They have a higher tensile strength but have to handled carefully because they corrode easier and can fail due to corrosion induced fatigue failure.

I'm choosing a new super-alloy called Custom Age 625+ which has the highest tensile strength of the materials and is immune to hydrogen embrittlement and corrosion.

We should have solid pricing this week on the 23RR engine.

 

Actually Martin, I'm not certain this is the case, and in fact, just the opposite may be true. Lower compression results in reduced thermal efficiency, which means more energy is wasted as heat than is converted to kinetic motion. More exhaust heat = quicker spool.

 

With higher compression you will have more torque. The expansion pressure goes up but I'm not sure how it effect the exhuas gas after EVO. That is interesting but one thing I am thinking is that the higher torque from the increased compression will drive the engine through the rpm band quicker under load and this sholdl spool the turbo. An example is here; I've played with igngition timing to see if I could bring the turbo on boost quicker. By retarding timing you increase heat and pressure after EVO (exhaust valve opening). This did spool the turbo quicker but the loss in torque actually made the car slower. I played with this on the dyno to see if I could get the turbo on boost with the lower timing and then bump timing back where it should be to bring torque back up and get more boost below the normal boost threshold. I had some small gains but it really wasn't worth it because again the torque you'd lose witht the lost timing. I had a few more psi of boost at 3K rpm but the time it took the engine to run through that RPM band of lower timing didn't benefit the power delivery in the end.

Now that I think of it I did build a few higher compression engine with no other major changes. We did a 2.0L with a big turbo and high compression and it made more power under the curve down low than the same setup as a low (8:1) compression engine. Now is it because of the increased torque from the compression or because of actually quicker spool. It would be an interesting test to hold two engine of different compressions at a steady state RPM on the dyno and do a boost response test.

 

subscribed.

 

Why must I torture myself by reading this thread on goodies that I will NEVER be able to afford?

 

Good work Martin

 

Prefered turbo with the RR is the 30R correct? Any testing planned with a 35R ?

 

It would make for an interesting test. I'd predict that changes in static CR, all else being equal, make for relatively small differences in spool characteristics in comparison with significant changes in ignition timing, based upon the fact that altering CR a full point (e.g. 8:1 to 9:1) typically results in ~5% difference in torque across the powerband, while moderate changes in ignition timing can affect power much more greatly.

Just a WAG . . .

 

can't wait to see the results on different turbo setups!!! Would this be a waste on a 50 trim?