rev limiter

[trax]

do we have one on the pd150? If not, anyone know where to get one?

Anyone else notice that if you give it some welly in first, it still likes to climb when you've dropped off the throttle? It acts normally in all other gears. Was pulling away yesterday , and was a little disturbed that by the time i stuck it in 2nd it had went over 4000

[basstard]

Well, IMO it should have one almost certainly. Every new car has one.

You should never nail it in 1st, just use it to move, then 2nd and nail down.

Dunno about the problem of 1st gear tho,,, I got a sort of a theory in my head but wouldn't like to say bs,,, displeased,,,

[trax]

yeah i dont really gun it, say i take it upto 3000 ish, (the first gear shoots up) then clutch in and stick it in second, the things hits 4000 before it engages in second, and i've not got grandad reflexes

wish i could knock the limiter down to say 4300.

Originally Posted by trax

do we have one on the pd150? If not, anyone know where to get one?

Anyone else notice that if you give it some welly in first, it still likes to climb when you've dropped off the throttle? It acts normally in all other gears. Was pulling away yesterday , and was a little disturbed that by the time i stuck it in 2nd it had went over 4000

Mmmm, a chance to air my theory

I've come to the conclusion that when ESP is on and you get wheelspin, the engine cuts power, but the unused boost that is allready in the pipeline doesn't get chucked to the dump valve, but instead gets thrown into the engine once grip is resumed and the car decides to give you more power, so even though you'e off the power the boost has to go somewhere, hence it carries on accelerating. I've nipped through gaps in heavy rain in traffic, nailed it, span in first, lifted off and started braking, then when the wheels have regained grip got a shat load of boost and shot upto the back of someones car!!!! Hence my pathological hate for traction control systems!

I'm getting the hang of these sensible post. I'm feeling almost... constructive...

P.S. No idea on the limiter - sorry!!!

[trax]

oooo, its wet outside and i need to goto asda, what a perfect time for theory testing

[aceman]

Not sure of the exact figure (cue PRC) but the TDI engines redline somewhere around 5K. They easily rev beyond 4K especially when revo'd so you can't be trying hard enough but it is always best to change up before 4k and make use of the available torque.

Regarding the overshoot in 1st I can't say I have experienced this although I have noticed at high speeds on a private road if you let off the throttle abruptly there is next to no engine braking so I am theorising that the ECU carries on fueling the engine slightly so that you don't experience any sudden braking action from the engine. Diesel engines have a high compression ratio so the effect of lifting off the throttle normally would be detrimental at high speeds.

I suppose it could be something similar you are experiencing when changing from 1st to 2nd as the braking effect would be worse in lower gears so the ECU tries to compensate not letting the engine die between gears.

[basstard]

Problem is mine doesn't do it,,, well, I'll try better and see but I'm almost sure it doesn't.

[pbirkett]

Mine does it if I rev it. BTW, nothing wrong with giving it some welly in first!!

[muddyboots]

I noticed it once, when I'd just got VAG-COM and was playing round seeing what I could monitor.
I was parked up, and blipped the throttle (a bit hard). When I took my foot off the accelerator the engine briefly carried on revving up, thought for a split second it was going to run away with itself and self destruct..!

(Did anyone ever see that episode of Scrapheap Challenge where that humungous diesel engine revved itself to bits?? Have been scared ever since!)

Regarding the rev limiter, I suspect the rapid tail off in power above 4000/4500 rpm acts as a natural limiter...but would imagine the ECU would have some kind of limit built in.

Vennuth -> Nice sensible post LOL... BTW, TDI's don't have dump valves...

[trax]

right, I've been blatting it.

It wasnt so bad today at all, but was a little noticable. It happens with TC OFF, ON and it is all fine. Since it was nowhere near as bad today I'm wondering if its something to do with the turbo and climate? Anyway, who cares, I'll just have to learn how to change faster

[magic77]

i found if you try to nail it in first in my tdi 110 whichis chipped good bye to tyres. IF I want to get away quickly just give it enought gas to start moving then when about 15mph nail it in second and car flies with little wheel spin

There was refrance to this over at tdiclub if i remember it can be sorted by the chip tuners through the map or maps ,some chips tend to do this and some of it is vnt surge.

[cpufreak]

limiter seems to be about 5100/5200rpm in my ibiza.
with mods, it pulls hard right the way to there...once FMIC is connected up, will need to find a RRday, to see the changes all my mods have made...