Engine response & rev matching

[astondg]

I went out for a drive yesterday in my 323i on some good driving roads near me. I noticed a few times when I had to go back from 4th to 3rd or 3rd to 2nd without braking or slowing down, like when aproaching a hill or a series of corners that I didn't need to slow down for, and I tried to rev match I kind of stabbed at the accelerator pedal to blip the throttle hard enough that it hit the floor (or the stop bit, full throttle anyway) for a fraction of a second and it was still about 200rpm short of a perfect rev match. This didn't happen when I was braking or slowing down because the rpm were falling quicker so I didn't have to match as big a gap between gears.

Does this happen to anyone else? I haven't noticed this on any other car that I have driven. My M20 should be slightly more responsive than a standard one too because I have no AFM or even MAF (it uses MAP) and I have a standalone engine management system (should be similar to those with the Zone Chip I guess?). I have noticed this happening worse when the engine is cold but it should have been warm yesterday, I had been driving for about 1/2 an hour before I noticed that. I have noticed it happen before too but I really noticed it yesterday because it interupted my driving when I was trying to enjoy the drive, it meant I couldn't get a smooth & fast downchange in that situation.

I know that there are some big gaps between the ratios in the gearbox and that doens't help but I still though that I should be able to do this?

Aston

[astondg]

I'm sure many of you rev match? I just want to know from someone with an M20 and possibly the standard gearbox (although still reply if you have the sport gearbox), that has done this before, if the same thing happened to them?

Thanks,

Aston

[johnono]

ive got the touring, so its a short ratio box, and a rediculously short diff, 4.43 or summin stupid like that.. i match on the downshift, quick blip and that,

mostly ive got it to about half a mark out, i.e if the sync is at 4k and im in 4th doing 120 kph, long corner, clutch in and blip up to 5-5 1/2 k and out all in the same movement it should setle in at 5 or so, but its all relative to the road at hand.. i dont rag it at all realy, as i only have this car, so if it pops im in the shitter

[6potWil6pot]

Hmm not sure if theres a difference between revv matching under braking or just while slowing down but i do know when ive messed up
Thinking about it i might rev a little higher when just slowing down. I'll take notice next time i drive!

[astondg]

So your engines are responsive enough to get the right rpm when rev matching without slowing down? Do you have to go full throttle (hit the floor/stop bit) for an instant?

There should be less of a blip required if you are braking because the rpm are dropping quicker.

johnono short ratio box should help. The diff ratio should affect the difference between gear ratios or the engine response with the clutch in, but that ratio . Must be anoying on the motorways? I have a 4.1 but the normal gearbox. I think the biggest difference between the two is 2nd to 3rd? So a 4th to 3rd change shouldn't be big difference? Sounds like you have no problem getting the required rpm for the match.

Aston

[Turbo-Brown]

I found it a bit difficult to match with a standard 'box. Didn't put it down to the throttle response though, just the massive gaps between ratios.

Didn't have too much problem if I was heel and toeing though so I guess that rings true with what you're saying.

3rd to 2nd was, as you say, the biggest problem as if it's not spot on, the car either lurches forward or feels like the brakes have been slammed on.

Never had to press the pedal to the floor though!

[astondg]

Guess it's just the gearbox then, so it's not just annoying changing up but also changing down . I think BMW could have put the sport box in all E30s, I'll have to see if I can find one near me. I just thought about it and it might have been a little bit worse than normal when I had to push the pedal to the floor because it had just rained while I was driving which probably cooled the engine slightly and my engine doesn't run as well when it's cold. It would still need a lot of throttle though. I haven't tried it since, I don't get to do that much around the city, I am normally braking when I down change (heel & toe like you said).

I hate that feeling when I get it a bit (or a lot ) wrong. Other cars I have driven don't seem to care so much. In my fathers Evo VI I can get it wrong or even not match it at all and as long as I am reasonably gentle with the clutch (nothing special, just don't dump it or something) I can barely feel the gear change (somtimes not at all). Unless I get it spot on in my 323i (and still be reasonably gentle with the clutch) it has that lurching/deceleration feeling that you described. It makes it difficult to be smooth. Any idea why that is? My father thought it might be because of the higher compression (9.8:1 in my 323i and 8.8:1 in the Evo) but I think I have driven other cars with 9.x:1 that don't do that as bad? Maybe not, I can't remember.

Aston