Christopher's 16v 2.5L 951 project.
#181
Instructor
Thread Starter
If i recall correctly - 944s stock cams. I had a modified set with even higher lift and different lobes but the machining on those was far from perfect so i decided to leave them and instead use stock n/a 944s ones for the time being
#183
This is an article I enjoyed reading about 4 cylinders and twin scroll exhaust.
http://www.epi-eng.com/piston_engine...technology.htm
http://www.epi-eng.com/piston_engine...technology.htm
Ok so forgive me if I’m misinformed, but it’s my understanding that the twin scroll design on a four cylinder engine is beneficial because it reduces the 180-degree exhaust blowdown interference. That interference is a problem at low rpms only. What is “low rpm” depends on the exhaust primary lengths and camshaft overlap. With little camshaft overlap and long exhaust primaries, twin scroll only helps at very low rpms. With very short exhaust primaries and high-overlap cams, twin scroll can help into reasonably high rpms. Like Kevin Igly’s four cylinder race car (not a Porsche), that thing has to big cams that it wouldn’t go well without both tuned primary lengths and teunnsctoll turbo. I guess I’m asking what kinds of cams are you running on this thing?
#184
Instructor
Thread Starter
In the last paragraph, the article cited by gruhsy backs that 180 degree interference is mitigated in inline 4 engines exactly by using a twin scroll (citation below). I would not say it's only relevant in low rpms, cause in practice utilizing twinscroll has sown significant spool time improvement on many applications. And faster spool means improvement in the whole range upward. Whether i will succeed or not is a completely different question
Although the split housing arrangement adds wetted area (hence boundary layer drag) to the gas flow, the advantages more than offset that drag increase. In instances where pulse energy recovery has been optimized, it is often possible, based on calculations using pressure and temperature losses across the turbine, to observe very high turbine efficiencies, which some experts say are in excess of 100%.
Pulses which are evenly-spaced but too close together will reduce the effectiveness of this pulse energy recovery. Apparently, that phenomenon is seen on even-fire inline 4-cylinder engines as well as on individual banks of flat-crank V8 engines, where the pulse separation is 180°. I was told that the ideal pulse separation was in the neighborhood of 240 crankshaft degrees, and that, on an even-fire (single-plane crankshaft) inline-4 (as opposed to the two-plane crankshafts used in some Moto-GP motorcycle engines) it is better to separate the end cylinders into one side and the center two into the other side of the turbine than to run all four together into an undivided scroll housing.
Pulses which are evenly-spaced but too close together will reduce the effectiveness of this pulse energy recovery. Apparently, that phenomenon is seen on even-fire inline 4-cylinder engines as well as on individual banks of flat-crank V8 engines, where the pulse separation is 180°. I was told that the ideal pulse separation was in the neighborhood of 240 crankshaft degrees, and that, on an even-fire (single-plane crankshaft) inline-4 (as opposed to the two-plane crankshafts used in some Moto-GP motorcycle engines) it is better to separate the end cylinders into one side and the center two into the other side of the turbine than to run all four together into an undivided scroll housing.
#185
Drifting
Yea I don't know if you really want THAT engine in your car. You know what, I happen to have a 951 totally built up with all kinds of cool parts and ready to test out a nice engine just like that exact one. You may think you really want that engine because all the hard work you have put into it but I know it's just no good for you without out being broke in by me in my 951, it told me. Trust me, I rarely lie. Oh yea, I'll give it back when I'm done "breaking" it in. Promise.
Last edited by Humboldtgrin; 04-16-2018 at 10:39 PM.
#186
Addict
Rennlist Member
Rennlist Member
Awesome progress. Congrats! What grade and wall thickness of stainless did you use?
#187
Instructor
Thread Starter
Voith - as far as i know it’s 1,6mm (~0.65in) and probably 304 grade stainless. Not the best for sure but should work and in time we’ll do an inconel manifold/titanium exhaust anyway, so this is more of a proto approach to see whether that tubing works as intended or not
Humboldtgrin - yaaay finally to get rid of the engine as soon as i finish the build was my intention since the very beginning! Give me a call and we’ll arrange everything
and honestly thanks for the support. I was completely devastated by the scammers.
Humboldtgrin - yaaay finally to get rid of the engine as soon as i finish the build was my intention since the very beginning! Give me a call and we’ll arrange everything
and honestly thanks for the support. I was completely devastated by the scammers.
#188
Addict
Rennlist Member
Rennlist Member
Who scammed you?
#189
Instructor
Thread Starter
let’s just omit that.. long story short a shop pretending they worked on the car while they didn’t, and most of their „work” turned out to be badly made junk, extremely hazardous to both car and people riding it. I don’t really want to delve into details on that..
#192
Instructor
Thread Starter
Simply put because of bang for the buck. Holset turbos are very reliable, they spool great despite their original application, and in this particular case i got a very good turbo in a barter for a couple of parts which basically were junk for me (i seriously did not even intent to sell them) it will most likely get refurbished, balanced and ceracoated so you can say this will be the only cost as far as the turbo is concerned. For every other turbo i would still need custom piping fabrication, so i don't count that.
Altogether the turbocharger will cost me around 300 USD and it will technically be better than new.. Can I get a superior borg or garrett within such budget?
Altogether the turbocharger will cost me around 300 USD and it will technically be better than new.. Can I get a superior borg or garrett within such budget?
#193
Simply put because of bang for the buck. Holset turbos are very reliable, they spool great despite their original application, and in this particular case i got a very good turbo in a barter for a couple of parts which basically were junk for me (i seriously did not even intent to sell them) it will most likely get refurbished, balanced and ceracoated so you can say this will be the only cost as far as the turbo is concerned. For every other turbo i would still need custom piping fabrication, so i don't count that.
Altogether the turbocharger will cost me around 300 USD and it will technically be better than new.. Can I get a superior borg or garrett within such budget?
Altogether the turbocharger will cost me around 300 USD and it will technically be better than new.. Can I get a superior borg or garrett within such budget?
But i see the bang 4 bucks part. I like your build, so keep the pictures and updates coming
Cheers
#194
Drifting
Could your exhaust fabricator make more? Oh and your intake fabricator make more? Say for a 3.0L setup? My 951 should be ready for that beast just as soon as your done. You really want a 3.0L not that one. In order to get what I believe you truly want you need to donate lots and even more then lots of money to the 951 Gods. Don't worry I'm here to help, myself.
#195
Instructor
Thread Starter
Humboldtgrin - I really want NEED your dealer's pharmacologist's number Don't you worry, as soon as this is finished, my fabrication wizard will cook me some very nice 3L 16v setup or maybe something a bit more exciting