4age Maximum Revs

[306rwd]

I aplogise as I am sure this type of question is asked over and over again.

I have an 4age AE92 engine used for rallying. It has a cam that is a bit too hairy but providing I can keep it up on the cam all is OK and the car works quite well and is successful in its class on UK forest events.

The spec of the parts is:

7 rib block with oil squirters
Standard crank - 42mm big ends
Wasser forged pistons.
Standard rods
ARP bolts and studs throughout
Firdanza aluminium flywheel
All fully balanced.

The engine is dry sumped.

This puts out a maximum of 190bhp at 8000rpm and has between 130 and 135 foot pounds of torque from about 5500rpm to 7400rpm.

I currently have the rev limiter set to 8500rpm.

What would be considered to be the maximum revs for this spec of engine?
Would it be safe to go to 9000 which would make a difference on a cammy engine?

Thanks

[oldcorollas]

when you talk about rev limits, above a certain point it there is no safe engine speed as such. ie, higher engine speed reduces the lifetime of rods and bolts.. the faster you spin it, the shorter(^2) the lifetime...

the ARP bolts will help a lot, the 92 rods are the beefiest/heaviest, and heavy pistons (??) don't help the rods but..

how long do your engines last at 8500? (edit: and can you afford to break one?)
are you still gaining torque up that high? or it is already falling off?

[oldeskewltoy]

valve springs... valve springs.... valve springs!!! You didn't mention anything about the valvetrain other then "hairy cams"

frequently a valve spring failure leads quickly to other parts going booom.

[306rwd]

when you talk about rev limits, above a certain point it there is no safe engine speed as such. ie, higher engine speed reduces the lifetime of rods and bolts.. the faster you spin it, the shorter(^2) the lifetime...

the ARP bolts will help a lot, the 92 rods are the beefiest/heaviest, and heavy pistons (??) don't help the rods but..

how long do your engines last at 8500? (edit: and can you afford to break one?)
are you still gaining torque up that high? or it is already falling off?

I have been revving these engines in different guises to 8500 in rally cars for years. I have blown 2 engines when I ran the bearings and this was definately down to oil surge problems which is now cured with the dry sump system,

Unfortunately I have to rev it to keep it on the cam when changing gear.

I have a dyno graph at this address HERE

[306rwd]

valve springs... valve springs.... valve springs!!! You didn't mention anything about the valvetrain other then "hairy cams"

frequently a valve spring failure leads quickly to other parts going booom.

I don't know the make of the valve springs but they have never caused a problem before at these revs. I also have one piece valves.

[30psi 4agte]

I cant see any issues with pushing it to 9000. I push mine up there quite often and its not dry sumped. I havent had any issues as yet........ not to say there wont be any

Im using pretty much the same bottom end.

[Sam_Q]

blacktop 20v excluded I thought the rod bolts where the weakest link in a 4ag engine? I hear they give you at around 9000rpm

[306rwd]

I guess steel rods would give me what I want, 9000 + a bit.

Rod bolts are ARP so hopefully they will be OK. Although I have been told that the originals are just as good as ARP.

[Sam_Q]

I have some cheap rods + arp bolts for sale but for 9000+ I dont sugest it

well I am honest

[oldcorollas]

i recon... give it a go... pull sump off and check bolts for stretch periodically.. maybe pull rods out and get them NDT'd for cracks (they are already shot-peened?) and if you see something bad.. swap... if it fails.. well at least you know...

[#rolla boy]

4age's love it up in those rev ranges, i know it is different but don't those olmpic series motors rev to like 15000rpm

[oldcorollas]

err... atlantic.. and err.. limited to 10500rpm..
and err.. light rods and pistons and low tension rings and light valves and everything else optimised for 10500rpm....

err....

[fixeruperer]

haha @ err...

[oldeskewltoy]

Atlantic engines are no longer Toyota... SOOOO many Atlantic builders are building WELL over the old 10,5 redline... some are reaching 14k!

[gixer]

I put Crower rods in mine, not real cheap but now I don't have to worry about stock rods!

[oldcorollas]

Atlantic engines are no longer Toyota... SOOOO many Atlantic builders are building WELL over the old 10,5 redline... some are reaching 14k!

on the 4A or the new motors?

how many minutes would you expect a 4A to last at 14000rpm?

[Sam_Q]

I am very far from being any expert but I dont see how any 4age engine could make max power above 11,000 considering the shape of the ports regardless of the cams.

For a reasonable build I still suggest spool rods as they are a very well made rod, strong as and a fair bit lighter than even a spindley blacktop rod.

[Rodger]

I do not about anyone else but I'd be changing cam specs to get a longer fatter torque curve.

Some good torque between about 5000 and 7500 rpm with max power at 7700 means it would be a lot less hairy and you can keep it in each gear longer.

Then there is less issue with engine life.

With the light flywheel the engine can still speed up and slow down quickly allowing good throttle balance and quick response.

Regards

Rodger

[oldeskewltoy]

all I said were some were reaching 14k.... that was the question.... max revs...

on the street... or even partial street... there is no need for an F/A engine.... Keep it under 9k and build as FAAAAT a torque curve as you can

[oldcorollas]

i thougth the question was... what is safe max revs for english forest rallying events
an FA engine is not appropriate for rallying either..

so you are saying that there is no problem going from 8500 to a 9000rpm rev limit on stock (92) rods and ARP bolts?