Jason Moyle Racing

There's a bit of an 8v theme at the mo!

I had a visit from Tim Moll (mitlom) last month armed with his budget track day toy. Tim was visiting his race car shell being prepped near by...well Gloucestershire isn't that far!...so Tim asked if I'd be game for giving the red rocket a last hoorah on the rollers pre sale.

This was another car that had done the rounds at various rolling roads, none of which really got the best from the 1900 8v, so much so Tim had a valiant go at playing with the fueling himself, with positive improvements in feel and fuel consumption but no figures to back up the seat of the pants.

After driving the car myself at Castle Coombe last year whilst testing Nick Penfold's racer in it's now old spec K jet form, Tim's car felt pretty quick and was a close match to Nick's when I was was driving!...sorry Tim couldn't resist!!...so on that bases I figured the power shouldn't be a million miles different and possibly better than Tim's last rolling road figure of 111hp at the wheels.

As Tim was brave enough to head Southwest bound we darkened the doorstep of AP Motorsport again. Now in all honesty neither Alvin at AP or myself are big fan's of K-jet with very lumpy cams...we spent 3 days on Nick's last year swapping metering heads and adjusting fuel pressures to get the best compromise as that is all you'll get on this system with big overlap cams, so as Tim's had a wilder cam than even Nick's we looked forward to making very little improvement over what Tim already had achieved!

We should learn to be a little less harsh on ourselves as after a couple hours of juggling fuel pressure and ignition timing we got a better fuel curve than we started with which helped Tim use an awefull lot less fuel going home than what was consumed coming down to us! The above combined with a bit of cam swinging netted a better idle and virtually identical power curve up to 5-5,500 where a couple of hp extra was gained. From there on in we had a positive increase at 6000 from 106hp to 112, 6500 came up from 108 to 114, with peak climbing from 109 to 117 @ 7k. Power was still hanging on well enough to push a little more to 7,500 where we saw a touch under 112hp up from the previous 106....pretty peaky on K-jet.

The odd thing was I expected to knock the cam timing back from it's heavily advanced position to find more low to mid range power, but retarding the cam...though actually giving it "less" advance as we had a lot to start with...knocked power off everywhere. To get the power increase I had to give the cam even more advance which gave the top end improvement without affecting the low end.

The trend I see is this...K-jet cars on tame cams like very little advance...i.e not much more lift at TDC on the inlet than the exhaust. When a big cam is added...sub high 290 to just over 300 degree's...they make the best overall power with a lot of advance. Cue open induction...the same cam, as in the case of Nick's Golf earlier back in the thread, likes a lot less advance for best spread & peak, the wilder the cam the closer to split timing makes the best power on open induction...I've seen that with other engines too.

This was yet another engine that went up the road very well considering the numbers, even tho the low end was down a fair bit over our road spec 1800's, and not coming alive until 6000 when the road engines are dying away. The moral is...don't over cam for road use...enjoy the low end grunt, don't fit big cams with K -jet unless regulations dictate so...even then, I believe as much or close to the same top end power is possible with a lot less cam but better head flow for a better overall power spread...if in doubt get the carbs out!...this engine would have no doubt benefited from open induction had Tim been keeping it...the next car / engine certainly wont have a breathing issue eh Tim...