Quote:
Originally Posted by kbrew8991
I'd be neat to see a "stuck with stock cams"/"external bolt-ons only" section  |
They take all the fun out of it.
Quote:
Originally Posted by kbrew8991
- custom header with some ideas garnered from Mustang drag racing guys that run stock heads to help out with scavenging exhaust out of these craptacular stock exhaust ports
- exhaust (short & light, maybe a muffler)
- intake (again, probably more weight reduction than power, but every bit helps)
- either Megasquirt stuffed into factory ECU housing or some sort of piggyback, not sure... (need to read rules again, but mainly for fuel curve adjustment)
- need to look again but I'm pretty sure I can mix & match stock parts (so 93 cams on 91 head, or just the 93 cams & head.. whatever is better)
there are also some small internal stuff I'm allowed (extra 0.5 compression ratio being the biggest help) but I'd be curious what the experts here would expect that to make with those 5 items attached to a stock 91 MR2 5SFE, or if I'll need to delve into doing all of that plus the $$$$$ minor internal stuff to squeeze every last drop out....
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For the header, I would take a look at your torque curve and decide where would be the best place to increase torque to help you be more competitive. You will not be able to raise your peak HP unless it happens where you are "on cam" but you may be able to negate some of the fall-off in the top end while still gaining some in the middle. What I just posted above should help you figure that out. If you bore it at all you need to redo the numbers. The 5SFE ports aren't too bad but still smaller then the pipe you will end up with. That is a good thing though. You will have a step that will help prevent reversion just try to line the bottom of the pipe up more with the port so there is more step at the top.
For the exhaust you want it smooth, short and just big enough around not to restrict you where you need it. I haven't seen any good ways to calculate that but I am guessing 2" or 2-1/4" pipe. The exhaust pipe size effects where you make torque as well using the same principal as the header I just don't know the formula for it.
An intake will help a little bit but the stock one is a pretty good size for the stock cams and VE. If you make one keep it as short as possible, like 16-18" while still getting cool air and keep it in the 2" to 2-1/4" diameter range. Also if they allow you to use a K&N style filter try to get one with a built in velocity stack or make one yourself. The rule of thumb for intakes is to get the air moving at about 180fps at your highest flowing RPM.
Definitely raise the compression to 10:1 and tune it with a Megasquirt. Jim Snodgrass got much of his power from tuning.
The 93 cams are probably a no-go. They take significant modification to put into a 91 head, either changing the base circle or changing the valves and spring heights.