Preliminary research on boost gains from multiple N75 valve sleeves...

[bhvrdr]

Well as you all probably know I have been testing multiple N75 valve sleeves gratiously donated by Greedspeed. As you will see by my results I am in no way inclined to sway my results regardless of who they were supplied by:

Test 1: Stock N75 valve on MTM Stage 3--

Vehicle boosted to a 21psi spike and held at 17 psi until gradual dropoff at 4600rpms

Wheel Horsepower = 203 hp
Wheel Torque = 252

Test 2: Size 60 (level 1) N75 sleeve --

Vehicle boosted to a 23 psi spike and held at 17psi with a gradual dropoff at 4600rpms

Wheel HP = 205
Wheel Torque = 261

Test 3: Size 55 N75 sleeve (level 2) --

Vehicle boosted to a 28psi peak and surged down to 17psi for 400rpms then held at 21psi until gradual dropoff at 4800rpms.

HP and Torque not yet tested but anxiosly awaiting.

Test 4: Size 50 N75 Sleeve (level 3) --

Vehivle boosted to a 24psi peak and surged down to 15psi for 400rpms until then held at 20psi until gradual dropoff at 4600rpms.

No testing is planned on the MTM stage 3 due to surging and confusing numbers that point towards this sleeve being far to aggressive for this already aggressive chip.

Results indicate surging issues with the best performing valve (level 2) but the gains appear to be solid and there is no evidence of overboost as has been documented by my buddy Jet.

I plan on investiging measures to reduce the surging (hopefully with the help of Dahlback racing) and will provide data as that occurs.

With regards to how this will perfor on your vehicle, that is entirely dependent on your tuners software and the headroom they leave for tweaking. Some software is simply better tuned than others.

Even spiking 28psi on the MTM I never ran into lambda values that were higher that +5 and 99% were between -3 and 1. There was only one or two outlayers in over 90 pages of datalogs that were at the +5 (well within normal limits). It does appear, however, that we have reached the limits of the stock MAF (flowing to 187-190g/s). That is another area of investigation (3" MAF).

Cheers! Mike

[DLSJ5]

Mike,

Did Jet use the same sleeves? Pardon me if you stated this already I'm kinda tired of reading today. So would you say the Stock N75 is the best? What did Anthony say?

[bhvrdr]

No worries,
Jet used a Dahlback N75K valve which I will also be testing this week. His valve eliminated surge altogether, but unfortunately peaked a bit to high and threw the car into limp mode. I have had no issues with overboost (and ive beaten this thing to hell) but am not pleased with the surging (am pleased with the boost gains however). Anthony is still collecting data from me and is not surprised as I am already running a chip that is tuned so damn well it makes it 10 times more difficult to get more hp out of. The nice thing is that even at the already high levels of boost the MTM puts out, the data logs show numbers that are similar to a stock profile as far as A/F safety is concerned. cheers! Mike