I finally have enough data to give a good comparison of a stock 745i vs our kit.
This line the graph shows the engines making the same rpm and the same boost level. It's not totally scientific but it's the best I have to date.
Both runs on same dyno but different days.
745i - good condition engine with auto tranny - 55F ambient
m30b35 - 100 miles on fresh motor with SEM - 89F ambient
I am not making any claims just sharing some data. It obviously isn't a perfectly fair comparison so take it at face value. 745i cam should make more torq than the b35 cam at this rpm.
Very impressive! Was the m30b35 in a manual or auto?
Also, I'm still fairly new at reading a dyno chart. When testing with a 5spd gearbox, should the chart show a bit more of a hp/tq drop between shifts than an auto or is there a way to minimize this?
Nebraska_e28 wrote:Very impressive! Was the m30b35 in a manual or auto?
Also, I'm still fairly new at reading a dyno chart. When testing with a 5spd gearbox, should the chart show a bit more of a hp/tq drop between shifts than an auto or is there a way to minimize this?
Dyno pulls are always done in a single gear and usually in the gear with a 1:1 ratio.
In this case the e34 was in 4th gear (manual tranny) and the 745i was in 3rd gear (auto).
5% is the generally accepted additional loss for an auto tranny.
Does the 745 have a lockup torque converter? I can't imagine only 5% through an open torque convertor, with a hydraulic pump and planetary gears. It really seems like the 745 should make more power than it did while it was making so much more boost unless the tune sucked.
It spiked to 4.5 psi more and still didn't quite match the output. That can't be right.
turbodan wrote:Does the 745 have a lockup torque converter? I can't imagine only 5% through an open torque convertor, with a hydraulic pump and planetary gears. It really seems like the 745 should make more power than it did while it was making so much more boost unless the tune sucked.
It spiked to 4.5 psi more and still didn't quite match the output. That can't be right.
It's a lock up converter. Consider that the 745i has a less efficient turbo, intercooler and exhaust system and it all adds up.
Dan, k27 is very inefficient especially compared to the turbos Todd's kits use. Plus dual 60mm pipes for an exhaust don't help much either. It made a big difference on my car when I put my custom dual 21/2" set-up on. Todd, do you have a picture showing the difference between your turbo and the k27?
