Xu5ja Race Engine

[TVH 0]

How much revs can the std bottom end take on a XU5JA engine? Of course it will be rebuild, balanced, ARP rod bolts, but std. crank, conrods and pistons. What will break first on sustained use over 8000rpm?

Edited September 12, 2008 by TVH

[Baz 421]

I hear they can happily rev to 8k, but i wouldn't hold it up there for sustained periods.

[wardy18 33 1 Cars]

Ive been told safely at 7k with double valve springs on standard bottom end, might up mine to 7500 then

[Grahamrally 0]

I don't know how hot this engine is likely to be, but to use over 8000rpm the head will have to be really good with a great cam and high compression. Then you're likely to kill the standard pistons from the compression pressures you'd need to run to gain power that high.

 

Rev limits are really set by the way an engine is built to and how well it's looked after, cooling and oil wise. I used to have a TU24 engine with 12.5:1 compression, ran standard liners and pistons with pockets and mad cam and constantly reved it to 9000rpm, and the thing that let it down was the fact there was a flaw in a brand new liner leading to a crack and a lot of serious steam out the back! lol

 

In answer to your question around 7k is about right.

 

Graham

[wardy18 33 1 Cars]

I must say as im coming up to my last event of the year an will no longer be running this block an pistons anymore im tempted to up mine to 7500rpm an see how it goes, running 10.9 compression ratio, standard skimmed head with rally catcam an double valve springs, vernier pulley, h&h dizzy on standard 1905 block with twin 45 webers

 

sorry to jump in on the thread, hope it helps to see what someone else is runnin, i have had no problems all year running at 7k rpm but the catcam really does was more rpm!

 

good luck with the build!

[brianthemagical 1]

When the limit is found, assuming it's not due to lack of asspiration or a mechanical limit, i.e minor valve bounce, it'll let you know by making holes in the engine. Or at least valve piston contact.

[projectpug 0]

Wardy- I can't see it being a problem if its only while accelerating throught the gears and not sustained in 4th/5th gear. What power you running with catcam on the standard head?

[wardy18 33 1 Cars]

If it was track running i would keep it lower but yes as i am only hillclimbing an quarter mile sprinting so not sustained acceleration in top gears, only seconds at a time, i know the standard crank can take 8000 but thats pushin it i think so 7500 will do fine

 

i only know from what ive been told as approximations with what i have as we dont have a rolling road so its more do a run, tweak it then see whats its like on the next run, have been told it approx 160bhp, no idea about torque!

[TVH 0]

Thanks for your replies! Your advice has been taken seriously. Also local engine builders do not recommend sustained use over 7500rpm on std bottom end. Instead of using very high revs, I've decided to build a 170bhp/7500rpm race engine. That should be safe enough. Race tracks in Finland are slow and twisty anyway so it will be mostly accelerating through the gears between the corners, of course this is perfect for a 205

Edited September 21, 2008 by TVH

[wardy18 33 1 Cars]

Jus got back from my 2 day sprint and hillclimb event an the engine an car ran so so well, i beat a 2ltr mk2 escort by over a second and engine revved flawlessly to 7500rpm and is still in one piece

 

good luck with the build mate

[projectpug 0]

In my engine waiting to go in i have a pt28 so good to know 7500 is easy doess it still want to rev more or does the power feel like its going?

[wardy18 33 1 Cars]

It keeps powering on, i cant remember exactly what the power band is on my catcam, im sure it was somethin like 3500ish to 8k

 

good thing with the aftermarket limiters they are jus so quick and easy to adjust

[projectpug 0]

Wardy whats the part number of your catcam?

[wardy18 33 1 Cars]

Ill have to find the bit of paper an let u know