cam choiceAfter some research on the US MR2OC I went for HKS 264 in and 256 ex
(both exhaust cams with the dizzy gears).HKS, because people on the US forum seemed impressed with the quality and reported that the cam timing was very close out of the box, and although the lift is increased, you can keep the original valve springs.my choice of duration - very generally, to make power with an NA engine you need big duration, and lots of revs. However this messes up your low-end, because, amongst other reasons, the increased overlap means that, at low revs, some of the fuel-air mix goes straight out the exhaust while both cams are open together. Also, at idle, some of the air that gets sucked into the cylinder can get pushed back out again, because the intake cam stays open so long. This really confuses ECU when it sees this on the MAP sensor. There are lots of other effects; it is said that the highest you can go with the stock ECU and just fuelling mods is about 272. So, for my low-budget daily driver plus occasional track cam install I needed fairly mild cams. HKS do 256, 264 and 272 cams. There are other manufacturers, you can go over 300 if you want.different intake and exhaust durations - There are different effects from having a slightly longer duration on either the intake or exhaust, I can't remember what they are now succintly enough to write it. I think that having one cam longer gives you the benefit of that cam opening longer without the drawback of the extra overlap you would get if the other cam was longer too, but I'm not sure if that logic is really true!both exhaust cams, because the exhaust cams have the gear for the dizzy so you can try using either cam on either side.CostsI imported the cams from the US for
$600, plus about $60 for delivery. This was back when the dollar was 2:1 to the pound so pretty cheap! (I've had these cams for a while now.) Fuelling is controlled by a 69p potentiometer from Maplins.InstallationInstallation was not too difficult.
You need the Haynes or ideally BGB, and a 10mm deep socket with a drive size that will fit on your torque wrench. You might as well change your timing belt at the same time. There are timing marks for both cam gears, the crank gear, and the dizzy, you just have to spot them. Oh and the 'seal packing' mentioned in the Toyota manual is silicone sealant.I had previously set my valve clearances before I installed my cams, set pretty close, but still in spec.
After installation, some valve clearances were a little further out, but all still in spec. With different camshafts! So I am very impressed with the quality and closeness to original spec of the HKS camshafts.by the way - I have the imoc shim bank if anyone wants itfirst startWhen it's all back together fire it up! move the dizzy around to get it to start/run.
When mine first started it had a lovely brap-brap-brap lope!tuning.
First, you need to get a ballpark ignition timing by moving the dizzy.
Move it one way and it will lope. brrrr-brr-brra-brap-brap. This is more retarded. Move it the other way and it will race with more revs. Brr-brrr-brrrrRRRRAAAAAAHH. This is advanced. Move it so you get a very slight lope for now and this will be safe. Note that the lope will go away somewhat as the engine warms up.Next, set the ballpark idle AFR, using the adjusting pot by the MAP sensor.
With hotter cams your idle will be richer because the ECU picks up the pressure from the air being pulsed back up the intake at idle and mistakenly thinks this is more air going into the cylinders. The idle AFR adjuster has 270 degrees of movement. If you bought the same cams I did, you need about 90 degrees anticlockwise (leaner). You can fine tune it later. You can turn it gently to it's endstops to find it's extents if you like. Note that at the extents, the ECU will think there is an open cicuit or short and just use the middle value, so you can't just turn it all the way to the end. (thanks JMR)Let the engine warm up to normal temp and turn up the idle speed adjust on the throttle body so it doesn't stall.
Now get your timing light out and set the timing.
If you can't get it to run at 800rpm for very long to set the timing, just get it close for now and then skip to the setting the fuelling accurately, then come back to the ignition timing. Either way don't do the screws up to FT yet because we can fine-tune it later.setting the idle fuelling accuratelyThe Toyota repair manual states in bold caps that you shouldn't adjust the idle AFR without a CO2 meter.
So you should probably go down to your local friendly MOT station. Or you can do it yourself, just adjust the pot until you get highest idle speed. Set the throttle body idle speed so it idles steady, and then make small adjustments to the AFR pot. If you still have the timing connectors shorted, this is good because then the ECU won't try to fight you and adjust the idle speed itself.Now, fine-tune the idle speed on the throttle body to 800rpm.
Then take it for a drive!It should be running pretty well at this point.
If not, double-check your cam timing. Maybe you skipped a tooth. I got my cam timing right so I don't know what happens if you get it wrong.fine tuning ignition timing on the road.If your ignition timing is retarded, it will run fine, but you'll be down on power a bit.
Throttle will be a bit less responsive. You will notice a big boost in power when the T-VIS kicks in, because the ECU advances the timing at this point (thanks JMR)gradually turn up the timing and you will notice more power, especially at the top end.
If you notice any of the following:very responsive to light throttle at low revs
(2-3k) but car bogs when using lots or full throttleno T-VIS kick
ECU can't control idle well
(bounces up and down again when it falls below 800)...then turn the timing back down again fuelling.The cams give you extra air at high revs.
You need some extra fuel. You could get something like a Greddy SAFC, or rising rate FPR, or even a mappable ECU. I used a 1k pot from Maplins, wired into the coolant temp sensor. The ECU thinks the engine is still warming up, and gives you extra fuel. My calibrated ar$e dyno suggested the sweet spot was a third of a turn when running at high revs (>4500). Below this it was best off (no extra resistance). A third of a turn is about 300 ohms which equates to a coolant temp difference of about 20 C (BGB). Not sure how much extra fuel this is. Let me know if you want to do this and I can tell you the wires to cut.
resultsThe idle with these cams is fine, with no lope, once you have got it set up well.
I actually get a bit of lope when I first start up. Low revs are fine, about the same. I think it's not so good below 2000rpm. From about 3500 you notice more power. 5000-6000 there is a lot more, and it revs all the way to 8000rpm without dropping off at all. I think peak torque has been shifted up a thousand or so rpm. A couple of months ago I replaced my wiring loom because the old one burnt out
(don't think it was caused by my wiring!) and because the pot change adjustment was so small I have left the replacement loom untouched. The results are, still good power, but it starts to drop off slightly from about 7000rpm. I think this is because the standard engine's torque starts to drop off at this point (from when I had my car dyno'd with standard cams) so the ECU is reducing the fuel at this point. But with the longer duration cams, it needs more fuel. I think I will get a spare engine temp sensor and cut the plug of my old loom, so I can wire in the fuelling control pot without cutting my loom... or maybe get a SAFC.....comments/abuse.
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yeah that's the HKS one 256 duration and 8.1mm of lift 
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