Rpm Limits Tu's What Spec Do You Have?

[christopher 5 1 Cars]

Just wondering.

 

A few people have been quoting power figures of TU's in excess of 7000rpm.

 

Since my standard limit is set to 7100rpm I am wondering what kind of specs people are running in order to achieve this safely....

[d-9 0]

Standard rev limit on the TU5J4 is 7250, mine is set on 7500 as it gives me a little extra room to play with (im running a very short box and tiny wheels) but seldom take it above 7000rpm so dont see it as an issue. If the bottom end dies I'll rebuild it, but dont see any problems as people are regularly take cammed TU5J4s to 8000.

[christopher 5 1 Cars]

people are regularly take cammed TU5J4s to 8000.

 

But are these standard TU's or modified ones?

 

Is the bottom end balanced? Are hey still running standard conrods bearings? cast iron flyweels?

 

The thought of a flywheel shattering at 8000rpm and flying through the gearbox casing is not a nice one..

[Sandy 189]

I've run 8v (later black tops) and 16v Tu's to 8000rpm regularly without any problems, very reliable bottom end. Rings seem to wear first, overfuelling is often responsible.

[d-9 0]

Afaik theyre all standard bottom ends. For some information on balancing cranks, check out this thread:

http://forum.205gtidrivers.com/index.php?s...93entry485693

[bren_1.3 1]

who was it that said theirs revved to 9000 rpm???? i think its on that pumaracing topic. these people cant be on standard bottom ends. no way.

[d-9 0]

As ive said, most people with cammed TU5J4s rev them to 8000 with no problems on standard bottom ends. Wouldnt fancy taking one to 9000thou!

[bren_1.3 1]

my setup hits 118bhp / 118lbft at the wheels at 6,400rpm, running on 95ron, which is 1.4 xs with twin 40s, 286cam (from germany) headwork done, I'm soon to be putting a newer head on after castle coombe for more I hope due to even more work done to it ,

 

mine will rev to 9,200rpm brens but we dont take it that high everyday due to the bottom end being standard (but fresh) also no point as the torque drops off alittle

 

 

new id seen it somewhere!

 

its not so much the bottom ends that will take the strain more the valve train.......

 

Peak power on the XS (TU3S engine) is at 6500rpm IIRC. Mine used to rev quite happily to 7k, and on a couple of occasions went over that. There were quite a few in Wessex motor club, consensus seemed to be they'd start to valve bounce at about 7.5k (no-one seemed to have any other sort of rev limiter)

 

always appeared to me that the 8 valvers weren't capable of more than 7500rpm. i couldnt find another thread by macaroni about valves bouncing on a TU3S at little more than 7000rpm. its all a bit puzzling to me, considering varying reports of valve bounce at differing rpm limits.

[stu_woac 1]

my car has only gone to 9200 twice on a rolling road on track it doesnt go beyound 8000 but goes there abit I would hence my bottom end has only 6000 miles done at this sort of rpms but no problems

[christopher 5 1 Cars]

always appeared to me that the 8 valvers weren't capable of more than 7500rpm. i couldnt find another thread by macaroni about valves bouncing on a TU3S at little more than 7000rpm. its all a bit puzzling to me, considering varying reports of valve bounce at differing rpm limits.

 

Well I have never experienced valve bounce on my TU up to 7100rpm..and this can be easily avoided with stronger springs I would have thought:-)

 

 

I was just reading a tuning book by a very respected expert in Fiat Twin cam tuning....a few quotes just got the grey matter reacting. Wondering how safe it is to rev up a standard bottom end to 8000+

 

 

Cast flywheels should not be used on engines above 7200rpm. Above this speed steel flywheels must be used because cast types are liable crack and break loose.

 

From this point of view it should be appreciated that an assembly which is run out of balance may survive a considerable length of time at modest rpm, but suddenly fail at a higher level, causing the flywheel bolts to shear (with possibly catastrophic results, ie death ir serious injury)

[Sandy 189]

The multipoint njection 106 black top heads have stronger valve springs.