Monday, May 18, 2009

General stuff

Been alot of wideband logging when using the car. Also cam timing trials.

I have pretty much found the sweet spot on the exhaust cam. I don't know what lift this relates to but it's simply using the vernier marks and swinging it slightly either way and assessing the engine's performance.

I know that advancing the exhaust cam, or giving it less lift at TDC, less overlap doesn't work at all at the top end, the engine is a dog, but it it does drive better at very low rpm and low throttle opening...I swang this around enough to know where is good or within 3deg at the crank anyway, I can percieve any changes by feel below this level. I have something to go on when I decide to get the car on the rollers and setup the ignition anyway...

I know advancing the inlet cam doesn't work from where I timed it. The top-end goes, as you might expect. Advancing the inlet cam means the opposite of the exhaust, more advance means it opens the valve earlier, more lift at TDC. This means also that the valve closes earlier, so top-end power is reduced as the fuel isn't "rammed in" at high rpm and you loose the ability to "ram" fuel and air in via the speed of the inlet flow, that last "cram" of gas into the cylinder. I have yet to conclude my tests here. I am currently running 3deg @ the crank more than I timed the cam at.

I do feel I have a good setting atm, a good spread or torque and power.

This was complemented on a private test track last night. I took the car to 7200rpm in 4th which is about 122mph I think, on my 3.89 diff. I didn't bother to hit 5th and carry on :) Car was still pulling pretty hard when the rev limiter took over it was accelerating well at this speed and should max out in 5th gear I think, somewhere around 150mph?

It's the best its been at the top-end, the mixture is also faultless from 5900-7300 holding a constant WOT mix of 12.7 air to fuel ratio. I have a funny mild lean out from 5400-5900 where the mixture goes to 13.3, which is ok but a tad lean for peak power. I have this mixture issue on all jetting and cam timings...I could use a stack of different trumpets to test, I could be getting some stand-off or flow pulse issues here?!

I also find that the cam timing has some effects on the overlap from carb circuit to circuit. I had it near perfect but it seems to be flowing a tad more with the current cam timing and needs some very minor adjustments. I am very close to cracking the jetting. However first I want to conclude my cam timing experiments so as to have a firmer idea of any jets I need to acquire. So it's balancing alot of factors.

I have tested lots of jets. I have increased the gas mileage alot by changing my jetting dramatically from where it was before I fitted the logging equipment.

Plenty has gone on, but I can be bothered to relay it cause most of it was not worthwhile. This is a totally unknown setup, unknown head, cams, exhaust, inlet manifold, carbs, etc. So I have to do the job of a major manufactoring company to get the results I want!

Lowered the rear-end back down to "dog with an itchy arse setting"...Tracking was all screwed after I raised it 1inch from where the tracking was setup! Rears been a bit nervous, also adjusted my old SPAX dampers on the back using a hammer.

This is the 2J1 wideband unit. Must say it's been faultess in a few hours of testing, good bit of kit! You can log of alot of data from it, EGT, MAP, TPS, RPM, VOLTS, Fuel pressure etc and log all this in software.

I will pickup the next caterham manifold I see on ebay and keep this for the future with an eye to making a 4-2-1 manifold and back to back test them sometime.

I have the logging kit running RPM, Manifold Pressure and Fuel Ratio, this is useful to see exactly where the throttle is and what the mixture is doing. I could use getting the Speed sensor on there also as load and rpm don't always tell you the right picture as more speed = more load!

Reasonably happy with the general performance atm. I made an error in trying to do some logging the other night when it was damp on the road :) I couldn't get any traction over 4800rpm in 3rd, just solid wheelspin to redline....I also had some wheelspin in 4th at 6000rpm...Interesting...2nd was just useless, basically just sit on the spot wheelspinning! It spins the wheels in 2nd at 6000rpm in the dry anyway.

I've been testing quite alot of stuff on a relaxed schedule. I had a persistant pump jet issue and tried 3 types of mechanisms and sorted that...I refuse to use a rolling road to setup the mixture and fuel, so this must be completed by logging and road testing as this translates into the right "feel" for the engine.

Above shows the software I have been using to log AFR, MAP and RPM.

You end up with something like that above...

You can then zoom it. Above shows a moderate acceleration in 4th gear, the MAP reading is high so this indicates an open throttle position in the first 2/3rds of the image. The ideal mixture for peak torque is around 13.2...Here shows I have around 13.2-13.1 during mild acceleration, so perfect. The MAP reading then lowers to 70 as I lift off and start crusing, closing the throttle a bit, the mixture goes to around 14.8-15.0...perfect!

Stoic or perfect combustion is 14.7 (where all fuel and all air is comsumed) and ideal cruise on this engine appears to be 15:1 or so to around 4000rpm. I have some leaner areas in a certain throttle location I will work on, but this is generally how things are at this rpm range.

The image above shows a WOT power-run in 4th. You can see my leanout in the 5700 range. The mixture from there up redline is perfect @ 12.5-12.8. The mixture before the leanout is fine too if you do a long 4th gear run from 3500-7300. I'm not that concerned 13.5 is ok, safe, if it was 14+ I'd be worried.

So I've been busy messing around with this useful info trying to get that best carburettor mix!

I want to sort the rear-end out when the engine is done, cause I will want to go and track the car.

I want to soften the front, down to 330-350lbs springs, it's too hard : 450lbs with an 87kilo engine! Need to sort a hood for it too...

Once that is done the car will be about finished. I'll be looking to sort a better gearbox and some more HP at some point, but no priority atm I want to polish the package first. I'd like to increase the rev limit now from 7300 as the top-end is better but the pistons might give up.

I've no idea how much power it's making. I've not much interest either...It goes fast but you get used to how fast things go don't you :) It's got a few horses anyway cause it was pulling nicely when it hit the limiter in 4th!

I've still not had to put a spanner on any of the work I did and the clutch slave job was perfect!

It's been giving me some decent payback last couple of weeks. However my batteries are still a bit drained. It's better now the engine tuning is coming together and I've got the equipment in to accurately read the dynamics, plus having done quite a few miles in it and nothing appears to be falling apart or suspect. That clutch job pissed me off.

I'd like to move forward from engine fiddling ASAP and start gathering the bits for developing some other areas and just snagging a few bits and sorting a few rattles etc. It was a nice break while I was recalibrating my brain to nicotine free.

I had a gander at the full drama's of the job ~ 2006-2009 on this blog earlier, what a load of work! Christ.

I can feel the "fasting" on working on the car has kindled some motivation I've not made anything or fabricated anything for 2 months, since the clutch job? I think I'll keep it cool for bit longer and work on some easy improvements to keep me hungry. Psychology is important in these big jobs!

No comments: