General Supercharger Thread

Next Tuesday :-(

 

Hit up Joseph @ BajaRex Motorsports in Orange. He recently installed my buddy’s Harrop SC.

 

Alright boys! First run! 5.58s!

Some additional information: done at 5500ft elevation which is 12psi of air pressure. My boost gauge read a max of 4.6psi, so theoretically the manifold pressure was 16.6psi! That is effectively 2psi of boost if you were at sea level

My "supposed" run before the Dragy of 4.4s was down the hill from my house at ~3000ft elevation which would be an extra ~1.2psi plus more air so the supercharger would generate more boost (I usually see in the ~6psi range). All of this meaning I'll do another run down the hill soon, where I get an extra 3-4psi right off the bat.

Truck setup: 35s, 5.29s, 3" lift, URD pulley with Magnuson airbox and K&N filter, HP Tuners with @ViktorG spicy tune

Air was 68F according to the dash, the MAF was measuring 72F right before I launched. Coolant at 192, tranny at 175.



Now hitting 4.4s and redeeming myself seems like a stretch, that's a full second plus quicker, but I'll have 20% more air pressure down the hill so hopefully I can get into the high 4s.

Also my truck has 276,823 miles on it

 

compare you launch to mine (G's)... those gears are launching you hard.

or I'm not pressing the gas pedal hard enough. (i need to do a better job of brake boosting)

but after your launch, you can see the effects of your elevation.

 

The launch Gs seem to be proportional to the gearing which makes sense and cool to see a "real world" comparison. Roughly 25% higher gearing and initial acceleration.

 

now look at the G's of the Plaid.....a monster.

 

Most impressive part is it maintains 1+ nearly the entire time too

 

gut wrenching

 

I think you probably just have to give her some more brake boost action. Mine on stock gears is more like @snivilous.

 

YES!!!!!!!

 

@snivilous do you find yourself ever having difficulty with the changing elevation, and this changing AFR and throwing codes? I’d be worried of it being too rich at elevation and too lean at sea level. At what elevation did you do most of your tuning with Viktor?

 

interesting. Why are your G's fluctuations so much? Trans slip or gear changes? and that big whallop you got at 25-30mph? is that 2nd gear?

 

I was wondering about this too, I was thinking it may be these crappy PA road imperfections jarring the truck around. This state is notorious for crap roads. 2nd gear happens in the 35-45 range I believe.

 

Not at all. And if my understanding is correct, it shouldn't fluctuate since the MAF is looking at raw air flow data, so for example the truck effectively thinks it's at 70% throttle at home versus if I was at sea level. It's just never accessing the higher flow rate part of the fuel map. I suppose there's the potential that the top end of the map that I never access is messed up, but Victor has it setup so it runs very rich at the top end and I assume just extrapolates out what is most likely to happen so everything stays safe and at a consistent AFR. But 70% throttle at sea level, versus WOT up here, should yield the exact same results since the air flow (thus manifold pressure) would be the same. The truck doesn't know any difference in elevation essentially.

But to answer your last question, I mostly sent logs from 5500ft at the house and I think one from a trip up the hill from 2700ft to the house since that's a long climb so he had some additional load reference.

 

I only ask because I saw on a Facebook page someone had issues that was tuned at sea level, and then was at 8000ft doing full throttle pulls and it was running so rich it fouled the plugs and ran like crap. Had to get towed. It was then suggested by the tuner to next time give it time to learn driving around easy at that elevation first, or disconnect the battery to force it to learn a fresh set of a parameters at the high elevation. Does any of this make sense if it’s supposed to adjust based on the MAF? Don’t know lol.

 

That sounds wrong to me, but as always, I'm not a tuner. Logically that doesn't make any sense though, you don't have to do that with a stock vehicle. As I recall most things go back to the MAF, so if it can read then it should be consistent. There's mountains around me over 11000ft and I've never had it run any richer than it normally runs up there, and likewise never had it run super lean at lower elevation.

 

Well, we need answers. Calling the expert @ViktorG for his thoughts since I’d like to know for myself if I ever drive across the country (especially towing) and find myself at high elevations. Most of the places worth seeing are at elevation, and we like to travel. https://vimeo.com/745486190

 

Another thing to keep in mind is the same octane fuel IS NOT available at elevation as at sea level. So if you're tuned to say 93 at sea level, you're only gonna find 91 at 5500+ ft elevation.

 

I found my stock pulley and pulled some measurements off it. Interestingly the bore doesn't seem to be tapered which I thought it was for some reason.

Pulley hub concept:

All 6061-T6, 12x 4-40 A286 bolts, helicoils on the hub side, 0.125" shear feature to react torque so the bolts are just keeping it from falling off, the pulley is bidirectional so as long as the hub is installed with the shear lug pointing forward then there's nothing to confuse. Hub has a 75deg taper to make installation easier. My thought is you wrap the belt onto the pulley, then just slide the pulley on so it'd be a lot easier than fighting the belt up and over the sides. First images are a 2.300" pulley (stock is 2.445", URD is supposedly 2.345") and second image is a 2.000" pulley.






And here is a straight press on 2.000" pulley.


I'm very tempted to buy the hub setup for some testing

 

Correct, however I thought you don't need the higher octane because your manifold pressure is less, thus you are less likely for knock to occur at elevation (assuming you don't increase your boost to compensate for it).

 

Generally speaking, you don't need to have the truck retuned for a different elevation.
The MAF will take care of things within the limits of its voltage output and the ECU tables.
You will just run less boost/air flow at higher elevation, and more boost/air flow at lower elevation.

 

Dropping this here cause I've been loving Jason Cammisa as a presenter https://youtu.be/LJP1K2Xo2oQ

 

Nice. My favorite chassis m3. I have one too with 36k miles.

 

Badass! This is going to be good

 

Damn that's low mileage! Mine has 110,000. Owned it since 75k miles. Mountain convertible cruiser

 

Apex wheels?

 

Yup! Downgraded from OEM 19" TO 18" wheels with fatter tires for road comfort. Also ebach lowering springs with Bilstein shocks/struts. Mishimoto oil cooler and electric (crank delete) radiator fan. Everything else has been shop replaced under a stupidly good warranty I got on it

 

And I’m in the 4s! By the skin on my teeth 4.99 with 1ft of rollout. I did 1 lone pass last night on a road that certainly looks like a slight incline to my naked eye. I’m convinced my Dragy is particularly bad at calculating slope. I also researched it a bit and it seems to be a well known issue, and it’s even worse on 0-60 runs than the longer passes. I’ll include a snippet from a BMW forum about it. People report it recording incorrect and inconsistent slope on multiple passes on a true drag strip. It’s annoying, I want my little valid stamp of approval on my run! Oh well, I’ll keep trying.

As far as the run goes, the cooler evening weather definitely helps! The G’s smoothed out a lot compared to the other run. I think it’s got more in it.

 

good run

 

Put like 120k on my SC Tacoma and never had a problem.