ix performance difference

[Earendil]

I have a stripped out chipped 4 door 325i, and a friend with a 2 door stock ix.
We swapped cars for a day so he could experience my awesome, and so that I could tell him his car was running well.

I've having a hard time knowing if it has all the power it should. I expected it to be weaker, but not as weak as it is. What gets me is that the engine is smooth, so every cylinder is pulling the same power. Also, spring maintance has been done (All filters, spark plugs and cap/rotor).

So now I'm trying to figure out what else is different. Wikipedia gives a weight difference of 160lbs. The tech section of R3V says it's 200lbs. That's a big difference, but not enough.

Is there an accepted value for how much additional drag the all-wheel drive system adds? Is it noticeable or negligible?

Has anyone driven an 'i' and 'ix' back to back and thought there was a significant acceleration difference? Are there any straight line differences between the weight and the extra spinning mass?

Thanks everyone. I don't want to volunteer to tune up and track down a problem that doesn't exist.

[Fraser]

200lbs is a big deal. I feel like my 318is is about as fast as my iX- a stock 325is should be significantly quicker. I haven't driven one of those in a while.

iX's are just kind of heavy and sluggish.

[Earendil]

200lbs is a big deal. I feel like my 318is is about as fast as my iX- a stock 325is should be significantly quicker. I haven't driven one of those in a while.

iX's are just kind of heavy and sluggish.

Thanks for the response.

I worked a few back of the hand numbers and came up with his car needing around 204hp to have the same power/weight ratio as mine likely does. I figure this based on his weighing 200 more than a stock 'is', and mine weighing 200lbs less. Add a 200 pound driver and give our cars a 10hp difference at the base, and 204 is what I came up with.

Or put another way, my car would need to be knocked down to 146hp to be as slow as his.

Perhaps this is the answer. I suppose I should find 400lbs of something to pile in my car and see if it's as slow as his :D

Do you, or anyone else, know what the drive train loss difference is between an 'is' and 'ix'? Are we talking 1 or 2%, or something in the teens?

[325ix]

I have the same delima. I just find it hard to believe that 200 lbs makes that big of a difference.

So, I was out driving today with my friend Lambo (Bishop's former car) and I noticed that my car was having a hell of a time keeping up with his car. We werent racing, we were doing the speed limit. I was following him and from a red light I was full throttle in 2 & 3 just to keep up with him. He said he wasn't all out, but was giving it a good bit of gas. For the life of me I can't figure out why I had so much trouble following him.

His car has no trunk tar, spare or passenger seat, but has the sub. He is also noticeably bigger than I am. He said that it was a 3.71 diff and had the mark d 91 octane chip.

My car has trunk tar, the spare, a passenger seat, and is an ix, but no sub box of any sort and I have crappy IE headers. It is somewhat tired and throws a check engine light occasionally, but I didn't think that would make that big of a difference. I have a cap, rotor, plugs, wires, coil and an O2 sensor on the way. Is that going to even the odds somewhat? I also have a 3.91 diff. Would the chip make a big difference?

I am in the process of buying this chip

http://www.r3vlimited.com/board/showthread.php?t=210051

He says that it will run on 91 or 93 octane. On Mark's site it only says 93 octane, 7000rpm, or 19lb injectors. Can you run this chip with 91?

[Earendil]

I am in the process of buying this chip

http://www.r3vlimited.com/board/showthread.php?t=210051

He says that it will run on 91 or 93 octane. On Mark's site it only says 93 octane, 7000rpm, or 19lb injectors. Can you run this chip with 91?

This is not a yes or a no. I run a 93 chip on 91 octane with no noticeable Ill effect.

[nando]

it's not 200lbs. it's just under 150lbs. it's not a big enough difference that the car would be noticeably slower. It would be like having a passenger in a regular 325i.

I have driven a totally stock, high miles '88 ix. it was SLOW. but it was a total pile of shit - everything worked, but it just didn't have any power. my bone stock auto ix would have killed it.

there is some additional drivetrain loss. I can't be sure, because I haven't ever seen a stock ix on the dyno. It's gotta be somewhere around 5-10% extra drivetrain loss. But still, it should only be around half a second or less slower in the 1/4 mile, because it has a slight gearing advantage to make up for the extra weight.

the '88 ix is also the heaviest year. it has a gigantic slab of trunk tar plus a steel spare that weighs a friggn' ton. Those aluminum bumpers aren't light either.

[325ix]

^ See, everyone is telling me that an ix is a fat pig that is insanely slower compared to the is. Mine has plastic bumpers now, and I think that my ignition is worn. Would removing the trunk tar hurt anything? I am always reading about people saying it will upset the balance of the car. Is this true?

I read that it is about .4 seconds slower in 0-60.

Also, Nando do you know if running 91 octane with a 93 octane chip will hurt anything?

[Kershaw]

yes. but do it anyway. its fine. trunk tar has to go. that's 50lbs right there.

my 89ix ran dead even with an 90i, both auto. and the i had a fresh top end rebuild. he put straight pipes on his i and then next time he slowly pulled on me.

awd system adds 146lbs iirc.

[325ix]

^Can that balance be restored with stiffer rear springs? I am doing GC soon, if I remove the tar, would 500/700 springs be good to help restore that balance?

[nando]

late ix's don't have trunk tar. I wouldn't worry about the balance too much, it's just dead weight any way you look at it.

and actually, stiffer springs would make it worse. you want to be slightly stiffer up front on an ix vs a rwd car anyway. my rates are 600/700, for example.

[325ix]

Ok, I am not worried about ride comfort, I don't want to have it ride like a wagon, but stiff is not a problem. I guess I will look at 600/700 springs.

[nando]

they are pretty stiff. you might consider starting at 500/600. you can always change rates later, since they're standard springs that everyone uses.

[nrubenstein]

It's significant and noticeable. Of course, it may have other issues as well.

[325ix]

It's significant and noticeable. Of course, it may have other issues as well.

Mine throws a check engine light and it also feels like after around 5k it dies and just stops wanting to go any further. When should it continue to pull to?

[325ix]

they are pretty stiff. you might consider starting at 500/600. you can always change rates later, since they're standard springs that everyone uses.

I just rode in a friends car (formerly Bishop's car) that had 475 600 and I had no problems with that.