My engine doesent rev more than 6000rpm. Other mazda engines we have build very similar to this one, easily rev to 8000rpm.

Other engines has been in "standard"cars and those has had MUCH longer exhauspipe.

Could it be that short exhauspipe causes this??! Has anyone else had problems like this?? My engine should have about 180-190hp and rev to 8000 now only 130hp and 6000rpm...

sounds a bit more drastic than just the exhaust if you've lost 33% power / 60bhp somewhere!

afraid I don't know the mazda engines, but assuming its runnung injection it could it be a sensor somewhere giving the ecu bad data that's messing the engine map/fueling up?

Ned.

Is there any form of rev-limiter? could this be different fromthe previous engines?

This engine has twin carbs 48 Dellorto's. No rev limiters. We changed different cylinder head+intakemanifold and carbs. no change. we have timed camshaft to many position. put more/less advance to spark. no change. air/fuel ration is correct.
Only thing we havent change is exh.manifold and exh.pipe.
I phoned to guy who made camshaft for me. He said it might be that ex.pipe is too short. It is only like 60cm and then there is silencer. He said pipe short as that will only work in high rpm's over 8000. not at all in low rpm's

it won't make 60 hp difference, that would need a cork in the exhaust!

try a free'er flowing silencer yiou could be getting a lot of back pressure pulse at thewrong time causing the engine not to breath properly. You could run it with no silencer at least it would sound faster.

[Edited on 13/6/05 by omega 24 v6]

I know it sounds obvious but have you checked to see if you are getting full throttle? I've lost count of the number of times I've come across this. Worth a check?

Silencer is straight pipe with holes in it, shouldn't cause too much back pressure.

Rusty: It goes to full throttle, checked few times Actually it feels/sounds like it wouldnt go to full throttle although throttle plates are full open. It sounds good to that point but wont go over 6000 it just stops there.

I will try to do longer exhaust system and shorten exh.manifold. We have rollingroad ourselves so easy to test if it does any good..

what ign system are you using?

Have the carbs actually been set up properly on a rolling road?? If not, then it could easily be your problem...

It has standard ignition system. It is electronic with distributor about 35 deg total advange, it has been changed..hmmm...could it be the Coil? It is new but you never know..
After all it took 6000rpm with 5th gear in race, that is 185km/h
Oh and I WON in first race and came 2nd in second race..after few spins.. My car has VERY loose rear, over steers very easily, have to do something to that too! That's probably because differential is welded to lock

flak monkey:carbs has been set up properly in rolling road. And when we changed the cylinderhead we took it from car which worked fine took easily 8000rpm we also took carbs and intakemanifold from that car..it is "standard car"with long exhaust.

Nice trophys we got!
Rescued attachment podium.jpg

You didn't get the high revs on the rolling road then?

I was wondering whether there was any sort of cold start rev limiter effect going on with the original mazda ignition. Does it do that perhaps? How sophisticated is it?
Perhaps there's a temperature sensor input missing? Is that feasible?

PS Congratulations!


[Edited on 13/6/05 by Dave Ashurst]

No high revs on rolling road.

Ingition system is from year 1983-85 so probably not very sophisticated..
It has no rev limiters. And it has been changed completely..no change..6000

Oh.

Is the rev counter working properly? Someone on the sylva list thought their engine was only reving to 5500 but it was in fact reving to 7800.