4A-GE Tune up

[apardal]

This topic might get similar to harkes' but I have somewhat different questions:

I might be able to reach a set of 264º 8.5mm lift HKS camshafts and I would like to know what to expect from them in terms of power output.

The items that I predict to install are the following:

- HKS camshafts
- Stock intake headers
- Fuel pressure regulator
- 4-1 TRD spec complete exhaust system or stock 4-2-1 with TRD spec secondaries and muffler
- 0,8 mm TRD metal head gasket
- some (little) head work
- stock ECU
- fidanza adjustable cam gears

now, the questions:

- should I go for 4-1 or 4-2-1?
- will stock valve springs be enough for the new lift? will i have valve floating at high rpm's?
- will I need to change the rev limit?

The car is for weekend and track use. It will need to pass MOT and my budget is limited. Please, help me with some wise options for this specific tune up!

Thanks a lot

Best regards from Portugal

[firehawk]

Quote:- should I go for 4-1 or 4-2-1?

4-1 will give you better top-end power but at the expense of some low-to-mid torque, so it's better suited for track use. 4-2-1, on the other hand, is a better choice for a car which will see equally both road and track use. Still, if your road use will be just driving calmly and then ripping it on the track, 4-1 may be the better choice anyway.

Quote:- will stock valve springs be enough for the new lift? will i have valve floating at high rpm's?

Toda recommends that stiffer valve springs and shim-under-bucket lifters should be used with cams that have 9mm or more actual valve lift. Also, TRD suggests that new OEM valve springs should be used with their lower-lift cams. A 264deg cam probably doesn't have significantly higher valve acceleration rates than stock cams, even with 8,5mm lift, so I believe that a set of new OEM springs should work for you. Check their price, though - if they're not significantly cheaper than a set of stiffer springs (such as the TRD N2-spec springs, 90501-AE851), go for the stiffer ones.

Quote:- will I need to change the rev limit?

I can't say for sure, but I'd think that in order to get the most out of your cams, you'd need to go up to 8000rpm. With the stock ECU, you can change the rev-limit by changing the ECU's crystal oscillator (XTAL) to one with slightly higher clock frequency. This'll also mess up the fuel and ignition timing somewhat, so you'd need to compensate it with adding a bit of fuel pressure and possibly retarding the ignition a bit by adjusting the distributor.

On the other hand, since you're already being quite close to what the stock ECU can handle, it may be worthwhile to consider replacing it with an aftermarket one to be able to adjust the fuel and ignition maps. If you're reluctant with using a full standalone system, a good piggyback such as the GReddy e-Manage will also work but you'd still have to modify the stock ECU to change the rev-limit (although in this case you could keep the stock FPR and and ignition advance).

[apardal]

Thanks a lot for your thorough answer firehawk. Do you have any ideas of the power output for this setup?

I've rechecked and valve lift is 8,35 mm.

I might advance with this soon, but without piggy back and running stock valve springs.

Best regards.