25 replies to this topic

[m1tch]

Hi guys, Just read a few threads around and apparently some rev limits are going to about 6800ish or over 6k, I know that getting to the redline is pointless due to the fact that it would have less power than a lower rev, but I just fitted a tacho to my mini and no way does it get to that.

Yes I have set it for a 4 cylnder car lol I can't get my 998 to rev much past about 4,500 - 5000 rpm, at 5000rpm (when it finally gets there) it doesn't sound happy lol so im not gonna push it more, just wondering:

1. Why my rev limit is lower than others
2. How I can make the engine happier to rev
3. What I can do to ensure that if I do go on a RR it doesn't keep running into the same problems top end

I know that they changed different parts with the A+ engine to make it rev better than the original 850 or 997s, mines a 1982 so im pretty sure its an A+ engine.

Why doesn't my mini like to rev?

[Pooky]

I think the figures you've given are about what you'd expect from a standard 998 to be honest.

To go higher you need to lighten and balance the internals and flywheel etc

[JohnGordon]

as pooky said i'd say thats about right. my 998 will go to about 5800 on the RR but on the road 5k is very rarely reached

[m1tch]

I will be putting in a 1275 engine in at some point, would a lightweight flywheel be ok for day to day driving? what parts can be made lightweight?

[Pooky]

The whole rotating assembly to be honest although you wouldn't want to lighten the flywheel too much on a road car.

Let's be honest, it's never going to rev like a Moto GP bike but a lightened flywheel, lightened crank and con rods, good damped pulley all balanced as a full assembly is the best place to start

[Ethel]

Valve gear is the chief limiting factor - stronger springs and a longer duration cam. Without some head porting you won't make the extra power from higher rpm.

[mini mark]

ive had my standard 998 over 6k as said not much power i find mine revs better when i have everythink running right just make sure all your ignition is all good points gaps and all that.

[m1tch]

Ah ok, I will have a check over of everything, need to get a colour tune to get the mix right, and also take it to a rolling road, might uprate the coil, is just the rotating mass the reason why it doesn't like reving? My car has had its head ported, but not much, I have no recipt for it being done either lol

[Ethel]

Rotating mass makes no difference to max rpm it just means it can be accelerated faster. The mass of reciprocating bits like rods and pistons can mean it's more likely to shake itself to bits. The valve springs not being able to keep up with closing the valves is the the first major hurdle but the points might start bouncing before that.

[mars red mike]

A poorly tuned engine is never going to rev well. Find the cams power band and use it. Revving the knackers out of it isnt going to get you anywhere.

[lrostoke]

are we talking freestanding rev's or driving underload revs.

You be able to go into the red really if just sitting in the drive reving it.

[mini mark]

i was talking about on the roads i dont see why any mini running well wouldnt reach it the timing isnt perfect but i dont think that will have to much differnece as long as its not miles out

[Wil_h]

As above, if you lighten all the internals it won't rev anymore. To get a higher revving engine you need to allow the car to breathe better. Any 998 with a stage 1 should have power all the way to 6k. If you want to go higher you need to start looking at heads, cams etc.

[jaydee]

My 998 with a cooper freeflow, an RC40 and a slightly ported head (also skimmed to achieve a 10,5:1 CR) revs fine to 6k/6,5k in first and second gear.
And without any valve bounce (havent fitted double springs yet).
As Wil h said, its the breathing and the cam that makes you car higher revving, lightening will only help to rev up faster.

[m1tch]

What does valve bounce sound like?