Xu9j2 high performace

[Mohammad208 0]

Hello

I bought this parts and i want to assemble a powerfull 8v engine

Aluminum 8v block

88mm crank

143 mm rods

Adjustable ecu

High compression flat top pistons

Catcams 4900366 cam

Xu9j2 head ported and inlet port size open up to about 35 mm

Diy inlet manifold with 58 mm tb

Gearbox

205 gti1.9 gears+ 16/67 final

And the last thing is exhaust manifold

Im confused a bit...

What size of primary and secondary pipe, i must use?

And what about stock manifold, is the stock exhaust manifold suitable for this engine?!

And the last thing is compression ratio, here in iran we have access to 87 octan gasoline

And i want to set compression ratio about 10.5 to 1, is that ratio ok with 4900366 cam?

 

Edited May 12, 2022 by Mohammad208

[petert 588]

87 ron or mon?

[Mohammad208 0]

It's ron number

[petert 588]

That's very low octane fuel then. Our minimum here in Australia is 91 RON and that struggles above 9.2:1.

Edited May 14, 2022 by petert

[Mohammad208 0]

So

What is your advise for compression ratio and other questions dear peter?

In iran with 4900366 cam and modified xu9ja engine, a few tuners make about 160whp and 200 n.m of torque.

I'll be happy for your advise for getting max power from this setup

[Richie-Van-GTi 72 2 Cars]

I have that camshaft, just been mapped today and have serious problems with flat spots at 2700 rpm and 5000 rpm, also couldnt hit peak power as it is running out of revs, still climbing at 7k.

We put it down to the cam profile with the plenum, it really needs ITBs and uprated valve springs.

That was 99 ron fuel and 11:1 compression

Edited May 16, 2022 by Richie-Van-GTi

[Thijs_Rallye 87 4 Cars]

6 hours ago, Richie-Van-GTi said:

it really needs ITBs

#

ONLY for dirt track applications and pro street use with adjustable engine management or carburettors

 

http://www.catcams.com/products/camshafts/datasheet.aspx?ENGINE_id=115&CAMSETUP_id=298

 

That's the reason why Catcams states the above. I have the 4900365 and that is doable with the original Motronic management.

[petert 588]

I can't see it being any good if it's 87 RON. I've done some Googling and it's very hard to work out exactly what type of fuel you have in Iran.

[Richie-Van-GTi 72 2 Cars]

3 hours ago, Thijs_Rallye said:

#

ONLY for dirt track applications and pro street use with adjustable engine management or carburettors

 

http://www.catcams.com/products/camshafts/datasheet.aspx?ENGINE_id=115&CAMSETUP_id=298

 

That's the reason why Catcams states the above. I have the 4900365 and that is doable with the original Motronic management.

I know exactly what catcams say, i have one on fully mappable ECU. As i said its just been mapped. It works, not saying it doesnt, im saying to get the best of it then it really needs throttle bodies as well. The big issue of the day was pulsing in the plenum causing flat spots making mapping very difficult. Image of my final run before he gave up for the day. The standard injectors were at 100% duty cycle so no more could be gained, also see the flat spots in the map.

Im putting something slightly milder in and going back with bigger injectors. There is more power available in the engine for sure. 

[DamirGTI 342]

If the petrol is so low in octane rating , and there's LPG readily available , i'd go LPG route with regards to fuel for such higher compression spec. engine . (LPG should be around 100/110 RON) 

 

D

[Mohammad208 0]

I run with that gasoline 9.5 compression ratio and no problem.

In iran we have gasoline, lpg, cng

I asked for the compression ratio because i want to know if i run that engine with 9.5 compression with high duration cam, its okay? Or will create problem for me

 

Edited May 17, 2022 by Mohammad208

[SRDT 182]

Is it really 87 RON and not 87 MON?

87 MON can be around 97-98 RON if not more so that's good for 160whp or a CR of 9.5:1.