Making an 84/85 MR2 competitive in SCCA IT: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Nov. 26, 2011 6:11 p.m. dean1484 SuperDork

My good friend has an IT prepared MR2 that he had been running since 1994 that I had been doing a lot of the mechanical / crewing on. Two + years back he parked it as it needed a motor freshening. He has since been driving Miatas and has made the statement that there is no way that we can make the old MR2 competitive.

However the new IT rules have changes since we were running it and I am wondering if with the installation of megasquirt with a wbo2, removing of the AFM and the tps and going to a MAP system and working on the throttle body to maximise air flow would be enough to wake this thing up a bit. I don't think I can legally do anything with the cams But I have not read far enough in to the GCR to figure this out.

Anyone got any comments suggestions. Is being competitive with an MR2 a lost cause?
Nov. 26, 2011 6:18 p.m. JoeyM SuperDork

I just sent this thread's URL to someone who races an '86
Nov. 26, 2011 6:30 p.m. jrw1621 SuperDork

The epicenter of all things MR2 is www.mr2oc.com
The site does require that you register (easy and safe) but once there you will find a sub-forum for Road Racing (as well as GRM Challenge, LeMons, Autocross and more.)
Nov. 26, 2011 6:41 p.m. dean1484 SuperDork

I am a member at mr2oc but wanted the collective wisdom from here on this.
Nov. 26, 2011 9:12 p.m. oldeskewltoy HalfDork

Getting a 4AGE to make power all depends on what you can... and CAN'T do.

I'm running a 4AGE with all Toyota parts cept cams (264 type), wrist pins, and injectors, and I'm cranking out a bit over 145whp.

So I ask again... what are you allowed to do, and conversely what are you explicitly NOT allowed to do?????
Nov. 26, 2011 11:39 p.m. Kendall_Jones Reader

I'm not 100% hip on the new IT rules, but I think megasquirt is legal but afm removal is not.

KJ
Nov. 27, 2011 12:44 a.m. mrhappy HalfDork

Could you do itbs with a plenum or a head swap?
Nov. 27, 2011 7:33 a.m. dean1484 SuperDork

The grey area is where it said.

"The engine management computer may be altered or replaced. A throttle position sensor and its wiring may be added or replaced. A MAP or MAF sensor and its wiring may be added. Other existing sensors excluding the stock air metering device, may be substituted for equivalent units."

So while I can add MAP I will have to leave the AFM in place. Could I alter it and remove/lock open the internals basically making it a tube? Yes it would be a restriction but with the internal flapper door thing removed and some strategic re working of it I am betting its restrictiveness could be greatly reduced. It is also kind of weird that they would let you add a MAP or a MAF and not eliminate the AFM.

I there is no rule about the limits of porting / polishing of the AFM. I have done this in the past with fantastic results.

See here>>> http://ehadesign.com/~dsmith/mas.htm

This little bit of porting and polishing on my RX7 AFM made a huge difference. Doing the same but either removing the flapper or just leaving it locked open opened up a lot of room for air flow improvements through it in the MR2. I think I have a couple of them in the parts pile and it would be interesting to see if there were differences between years. I would be especially interested in the castings to see if one had more meat / thickness to work with versus another.

I think I am stuck with the stock cams but I will read on.
Nov. 27, 2011 7:44 a.m. Streetwiseguy Dork

IT rules : "If it doesn't say you can, then you can't" No cam swaps, no porting. Engine prep is limited to blueprinting, .040 overbore, and minimal head shave, IIRC. Throttle body cannot be altered or bored, stock air metering must remain. The air intake must draw its air from the factory area- if it pulls air from underhood, thats where you must draw your air.
Nov. 27, 2011 8:02 a.m. dean1484 SuperDork

I just read back in the rules and they way they are written is that although you can go to a MAF or MAP based engine management system and the addition of sensors is ok the stock metering device must remain and it is very specific that the stock AFM can not be modified in any way.

This basically kills the deal trying to make the MR2 competitive in SCCA IT. I still may do the conversion just to see if there would be any improvement. I have dyno numbers when I tuned it after the last freshening. So I can see if the swap over to MS does anything.

With out any way to reduce the restrictions of the air flow in to the motor there is no point as the AFR's were perfect. So adding fuel would be the only gain. I am also stuck with the stock distributor so you really can not alter the spark curve.

About the only thing i could hope for would be to broaden the power band giving it more grunt out of the corners with some tweaking of the fuel maps. Something that the drivers of this car have always commented that it was lacking.

Dang it I was really hoping that this little car that has had such a great run in SCCA could possibly be made to live on. At best in its current configuration it is a mid pack car.