Xu9J4 / Cat 4900528 Camshaft

[mollisk 2 1 Cars]

I have installed a pair of Cat 4900528 cams to an XU9J4 engine which is also fitted with 45 DCOE's. On the rolling road, the engine gives a maximum power of 149 bhp at 7250 rpm ( at the wheels ) and maximum torque figure of 140 lbft at 5500 rpm.

I was a little disappointed with these figures, as when the engine was originally built with standard cams it was set up on an engine dynamometer and gave figures of 178 bhp at 7000 rpm and 140 lbsft of torque at 6000 rpm.

I realise that comparing figures from different dynamometers is not really possible, but I was expecting approx 190-200 bhp from the engine fitted with these cams.

 

Cat Cams 4900528

 

282 / 277° In / Ex Duration @0.1 mm clearance

 

11.50 / 10.75mm In / Ex max lift

 

2.70 / 2.40mm In / Ex lift at TDC.

 

Does anyone have any experience of using 4900528 cams in an XU9J4 engine ?

 

 

Regards,

 

Kev M

[Anthony 1,000]

Obvious question is did you time them up properly with verniers to the manufacturers specs using a dial gauge or similar?

 

Have you touched the engine internally or is that all standard? I'd guess that those cams would probably benefit from more compression as on paper they look pretty hot judging from the duration @ 1mm, and I suspect that they'll want a fair bit more than the standard 10.4:1 (assuming it's a D6C you've got) to give their best. I've no experience with that particular camshaft though, only some of the milder grinds that Catcams offer that do work well enough in an otherwise standard engine.

 

All that said, 149hp at the wheels sounds reasonable though - a standard Mi16 seems to give around 125-130hp at the wheels from what I've seen.

[mollisk 2 1 Cars]

The cams were set up as per the manufacturers recommended figures. The head was skimmed, but only to clean the face up, by approx 0.010", so the compression ratio may not be optimum for the duration of the cams.

The engine pulls cleanly through the rev range and the air fuel ratio, measured from a lambda boss in the exhaust, is also good throughout the rev range. The engine timing has been set at 34deg full advance. ( NGK BCP7EV plugs )

 

Regards,

 

Kev M

[craig_007 1]

I'm not the most qualified to comment on full adavance but on an MI thats alot.

 

My full load adavnce is 26 degrees.

 

149 at the wheels is around 185 fly I'm guessing, Did you try at all retarding the full load advance ?

 

When I had carbs on my MI I run 32 degree adavance(distributor) as I didn't know any better, After reading a few topics on here and getting responses from people who know there stuff I backed timing off on my next visit to the rollers and if I remember correctly I gained approx 10bhp.

[andy0075 9 1 Cars]

I think your timing is complete out of range. I meassured the output power from my

MI D6C fitted with PeterT cams and 45mm throttle bodies with diffferent sparkangles

on the rolling road from 30° to 24° and 26° gives the optimum on my engine .

 

-> same as craig_007 :-)

 

150 bhp @wheels / 185bhp @flywheel with standard bottom end and standard head/valve

sounds ok for me.

 

Andy

[brumster 135 1 Cars]

I've got the 528's in my spare engine, an otherwise-standard XU9J4 apart from the head skim and the grinding to the head for the followers to clear. It was also never dyno'd but my bum-dyno never complained.

 

I've got the old map on my work laptop here, so I've quickly looked it up.

 

WOT advance curves up to 26 in the midrange then backs off a little to 24 higher up. There is peak of 28 degrees that's centred around 50% throttle around the 6750 mark (again, centred really). But nowhere on the map does it go over 28, that's for sure... if that helps? It was also timed to Catcam's specs.

[petert 554]

149hp (111kW) at the wheels I would have said is on the money for an otherwise standard engine on carbs. From my experience, that spec on 45mm TB's typically run anywhere from 107 to 114kW at the wheels (DynoDynamics). We only talk in power @ the wheels in Aus., so the flywheel numbers are meaningless to us. Having said that, I recall a thread by Mattsav, where he dyno'd an XU9J4 with 528 cams and achieved 195hp flywheel. You didn't say how ignition is set up. ie ECU, 8V dizzy etc. Most people have little idea of how to find TDC on an XU9J4, so if your hp is accurate, the 34 deg. is possibly 26 deg when measured correctly. If not, there is more hp to be found by dropping to 24-26 deg. as previously said.

[mollisk 2 1 Cars]

Thanks very much for the replies to my post, it would appear that some gains in power, and hopefully torque, could be made by retarding the ignition to approx 25 deg.

 

The ignition utilises a 1.9 8V distributor. I located TDC on the engine by using a dial gauge on the piston and a camshaft timing disc on the crank with the head removed. The "dwell" period on the dial gauge at TDC was measured with a pointer on the timing disc and TDC marked on the flywheel at the mid point of the "dwell" period.

I will try reducing the ignition advance to 25 deg to see if there is any more HP to be had.

When the engine was originally dyno'ed ( with standard cams ) the ignition was set to 8 deg at 1000 rpm, unfortunatly I did not take a note of the figure for full advance.

 

I will not be able to do anything with the engine for 2 weeks, but I do have copies of the dyno sheets for the standard engine ( engine dynamometer ) and cammed engine ( rolling road dyno ) which I will try to post.

 

Thanks again,

 

Kev M

[unariciflocos 49 1 Cars]

The ignition utilises a 1.9 8V distributor.

 

Calling that a bodge is a euphemism around here. Just get a proper ignition system.

[mollisk 2 1 Cars]

Update on the above.

 

I have since fitted a DTA s40 ignition only ECU and programmed it with a map which Perter T posted on here. I havnt had the car on a dynanometer, but the difference when driving the car is like night and day over the 1.9 8V distributor which was fitted.

 

Kev M