Need DA supercharger advice...

[bimmerbot]

Got a question for anyone with a Downing Atlanta supercharger -- or for anyone who doesn't, but can give me an informed opinion. http://www.happytogether.com/318ti/forum/smile.gif

I'm pretty set on putting a DA on my '98 ti sport in the late winter/early spring timeframe, but for right now in the present, I'm looking to go to 17" wheels and also lower the car (most likely on an AP/Koni setup -- nice prices on those over at nikis-place.com right now).

Now, based on what Tire Rack has told me, the widest tires I can run on 17" rims is 215/45-17. By searching through the archives here and on other boards, I see that some folks have run 225/45-17s with no problem (i.e., no rubbing), even when lowered.

I had originally planned on going with the 215's, just to steer clear of the whole rubbing issue.

But now, I'm wondering....with the increased torque after the supercharger is added, will 215's be insufficient, width-wise? Will I need more grip?

I'm hesitant to roll my fenders, but if that's the price of adding power, then so be it.

Any experiences or opinions to share? Any advice is appreciated.

[J!m]

I was looking at one point for the largest tires I could squeeze under my car.

A visit to the Tire Rack showed me that with Mille Miglia MM11-2 sport wheels in sizes 18x8 in front and 18x9 (option) in the rear, I could go to 225/40 18 in front and a HUGE 245/35 18 in the rear (that's at least 8.5 inches of rubber on the road). The big problem is the rear tires, which are a Corvette size I think, and un-common. This leads to the tires costing far more than the wheels...

This set-up fits the ti with the factory sport (lowered) suspension. I do not know if these wheels are available still, as I have decided to go with forged BMW M3 wheels.

I don't think a ti with a blower (~205hp) will spin those monsters too easily...

------------------
"Speed's just a question of money. How fast you 'wanna go?"

[ayton]

my friend has 245/40/18 lowered on H&R's on a 9 inch rim no rubbing 3 people in the back of his ti!

check out pics of his car here http://www.dtmpower.net/ppost/showgallery.php?cat=500&stype=1&thumb=1&si=Genie_Tinik

[surge82x]

Personaly I think it works very well. I've got the DA on mine with 215's and lowered on H&R springs. The only problem I've had as far as laying the power down in the diff. currently I'm looking in to getting an M3 diff to replace mine. From what I've heard about that, it seems to work very well. Food for thought.

[bimmerbot]

Thanks for the advice. I'd read that swapping in an M3 clutch is a good idea, but hadn't read anything about switching differentials. Makes sense, though.

Are you still using the stock clutch? If so, what's your experience been?

[ayton]

FYI fellas...you cannot use an M3 diff in a ti.It will not fit, they are two entirely different units...If you want to switch diffs you need to get one from an M coupe or roadster (Z3 family) they are bolt-ins. To save some bucks you can get an E30 diff and with a little sweat you can get it to work. But also it's not just a matter of swapping out diffs ...You need the right one, waht you want is an LSD. 3.45/46 LSD works best and I've heard of 3.64 and 3.73? LSD's working out great keep in mind there are trad off's the higher you go like higher running rpm's and such which will make an already high reving buzzy motor more so. 3.45/46 LSd is the best (stock on the club sport)

[Syndicate09]

:D

Whats up all reading this!! Names John Jordan, been working on my ti for a long time, check it out in the gallery!

Ok well I've got some meats on my 17"s and before I did any other work I had the Supercharger and the Supersprint cat-back system on it and it would spin those tires pretty easily. Dont be fooled that kit is amazing, and with the intake and exhaust its more like 220hp, so it will move.

My ti has been in the shop for about a year now and with all the mods it should round off to about 300hp at the rear wheels. ( keeping my fingures crossed, thats what we're hopeing ) So if you need any info or advice just look me up. Later all.
John "BUZZ" Jordan

[fourbanger]

300hp to the wheels?

good lord, what the heck did you do there?

Are you getting the DASC to boost more? If so, how did you get it to do so? Pulleys?

just interested..

still not sure if I should go turbo or sc..

[J!m]

Fourbanger:

If I were you, I would go with the blower over the turbo.

There is less heat-rise from the blower, as the exhaust does not have to pass right by the intake air AS IT'S BEING COMPRESSED (creating heat)...

Plus the D/A kit is quite nice. I gave it serious consideration before deciding to go with a motor swap myself. (and a warranty is always nice)

PS: 300 AT THE REAR WHEELS sounds a bit off. I'd not only like to see the dyno chart, but I'd like to be there for the pull before I'll buy into that...

Let's work it:
Let's be generous and say the D/A will get you to 210 at the FLYWHEEL (this would be a 'factory-fresh' motor). Lets also say you swap pulleys and/or rig the by-pass for a bit more boost. I'm guessing around 220 TOPS with this before the knock sensors retard the timing to the point where the motor won't run. A free-flow exhaust should be good for 5 or so (the stock ti exhaust is not bad, which is why I never bothered to replace it), so now were at 225 at the flywheel-not bad at all. At this point there are no options but custom software, or complete custom engine management. With the software tailored to that particular engine, I think 235 is realistic (on pump gas for all this, right?). I was thinking a custom-ground set of cams might help, but most likely only on the exhaust side. All the air/fuel that little motor can use is being forced down it's throat... Let's give it another 10 hp for giggles and/or error.

SO, 245 is all I would hope for (and it will CERTAINLY cost more than a six conversion when it's all done- a big part of the reason I decided to swap) I have the 3.2 with the dinan stage I chip and a lightweight flywheel (no other mods- even the air box is there), and I can conservatively say there is a peak of 250 at the flywheel (based on Dinan dyno pulls). A (un-molested) blower on this motor brings us up to around 360-370 (at the flywheel on pump gas). There is a weight advantage to the four. I'll give it that. But the sound and torque of that 3.2 is VERY nice... QUITE addictive.

In any event, there is mechinical loss through the transmission and differential. Moving oil takes energy as well as friction on bearings and gears, which is one of the reasons why synthetic is the way to go in the diff and tranny. Dyno pulls prove gains by changing oil. Any car can benefit from this "free" HP.

If I remember correctly, as much as 20% can be lost to the drive line, but I may be off with that. It just doesn't add up to me.

Final score:

HYPER 1.9= 196 at the rear wheels
Stock(ish) 3.2= 200 at the rear wheels

Should be very close in 'feel' (AKA butt-dyno) but I think the 1.9 will cost more money. There is a certain cool factor with being faster than a factory M3 LTW with less than 2 liters. I'll give it that.

OK. That was fun.

J!m
[/u]

[bmw///m3///]

what about a wipple supercharger ???

is it better than DA? its more widespread use by all manufacturers

[Dredder]

Syndicate09,

Give us an update on your car. Have you achieved your goal on getting more horses in that badboy. What are you doing to it thats taking a year? What mods have you done so far. Inquires want to know....

[GDB]

I would go with atleast a 235 wide tire. Unless you are driving on R compound tires a 215 just isn't going to give you the contact area you need to really put down that power. I know the 205's on my car now are definately not enough and I'm stock. You will have no rubbing problems with a 235 and it will definately help you make use of that power. Good luck man.