Intro To Performance

Authored by: Nybow

I am ---- I’m from Staten Island, NY and am getting an mr2 supercharged, with 164k on the body and 54k on a rebuilt motor + tranny and brand spanking new clutch and a lot of other stuff new with all receipts Sunday. This is my dream car and I have dreamed about it since I was a little kid. Now that the car is mine I have a few questions. Can I put a blow off valve on this supercharged car to make that sexy whoosh my Rx-7 and eagle talon tsi made? I know this seems dumb, but I am not sure exactly all of the particulars of a supercharger. Second, how do I put a boost gauge on this vehicle any tips or tricks or gauge recommendations.

1. BOV - On the SC motor, there is already a Bypass valve in place that has two functions: When the SC is off (anytime the engine has more than +5" of vacuum for more than a few seconds) it opens and allows air to bypass the supercharger since it isn’t spinning. When the SC is on, it acts as a BOV if the boost gets over 8psi. If you put on a bigger pulley, you have to modify the vacuum routing to the valve so that it won’t vent boost over 8 pounds. People have tried modifying it to release the boost between shifts, but it doesn’t really make a performance difference. Unlike a turbocharger, an SC doesn’t have to deal with compressor surge or spool. It’s either on or off, and if its on it’s boosting immediately. With this in mind, it would be pretty pointless to put a BOV in the system. Also, the throttle body comes before the supercharger, so there isn’t any boost building up before it - which is what a BOV is supposed to vent. If you can figure out a way to make it go “Whoosh” then go for it, but it won’t get you performance, and it may require you to manually wire up a constant on for the SC. If you really want a BOV, put a turbo on it!

2. Boost gauge - you can plumb a boost gauge in just about anywhere after the throttle body, but I would recommend going to the plenum just before the intake splits off into separate runners and then either drilling/tapping a port to put in a fitting (Autometer used to make a kit, but you pretty much just need some fittings and thin nylon hose), or try and find another hose that comes off of it that you can tee into.

3. Performance - There is a lot you can do… everything from a K&N air filter, to ditching the SC and going turbo (or keeping it and doing twin-charged)! There is so much information. Basically, my preference, should you choose to stay SC, would be to get a nice free-flowing air filter attached to the AFM, and then get the NST Kit #NST04180K. It’s $289, but ups the boost from 8 to 13 psi. Believe me, it’s enough to make you seriously consider switching to the turbo. Adding water injection before the SC is another way to get a little more oomph as it will help the rotors seal, and keep the air cooler - just don’t want to put too much water in. Upgrading the intercooler to an air-to-water and getting a good exchanger up front helps a lot too. A free-flowing exhaust will only net you maybe one or two hp, so don’t go spending lots of dosh on a mellon cannon. Put some money into the suspension first. Improve the handling before the horsepower!

Right now the engine is stock, N/A, and distributor based ignition system. I can’t be for certain but I’m sure that the engine is the original, the car itself has 140k miles on it. The problem I’m having is I’m trying to decide if I should just invest in a different exhaust manifold and other minor upgrades, or if I should try doing a swap to a 4AGE 20v engine. I’m also open to other suggestions that don’t require a great degree of complication since this will most likely be my first project. Something I should have noted is that I am pretty confident doing electrical wiring of any kind, as long as I have some schematics to follow. If I go the 20v direction I’m planning to at least try for a CR slightly higher than stock, but I’m hoping to keep the timing the same as stock so I can use the swap ECU to get a feel for the engine before doing anything drastic.

So I’m looking for an MKI and a reasonable engine swap… now, I know the laster MR2s can come with cool stuff like t tops and what not, but I’ve also heard that the earlier ones are lighter and handle better… also id like to do an engine swap to make more power… and I’m really not sure which engine id like… preferably something that won’t cost me an arm and a leg, and preferably something that won’t be too complicated… I had my eye on the 20v swap, but if it makes all of its power at the top of its rev range that just doesn’t seem as good as it sounds… to the idea of it revving to 12k makes my quivver :x even if it would cost ridiculous amounts…

Put some consideration in before deciding to do the 20v swap. I mean, it’s not that it’s really hard, but you will have to do some fabrication to get coolant and exhaust to work right. If I remember correctly, the mounts are the same, so it should bolt in ok (You’ll need to use your stock flywheel if you want to use the tranny already in the car). There is a lot of electrical work in getting a 20v to work, and if you’re good at electrical, but not very experienced at in-depth auto work, I wouldn’t attempt it - I mean, I know these cars inside and out, and a 20v swap still intimidates me. The 20v doesn’t rev to 12k though. The silvertop is about the same as the 16v, and the blacktop will do 8.3k. The 12k motors are the formula atlantics - be prepared to spend a lot of money, and have horrible drivability (unless you live in the plains and never have to go below 50mph or 6K rpm for anything).

Building an NA motor for lots of power requires a lot of money. There aren’t really a lot of performance bolt-ons either. At heart, the 4AG (NA) and the 4AGZ (SC) are more or less the same motor, minus some small changes. The 85/86 does have some differences between the 87+ motors (which include the supercharged), but they’re not too critical. The 4AGZEs had oil quirters under the pistons which helped keep them cool under boost. A 4AGZ swap is a bit of work, and require some definite mechanical and electrical knowledge, but it’s the best way to get some performance without spending a huge amount of money. Also, the 85/86 NA used a C-50 transmission, and the later NA’s used the C-52 both of which are pretty much interchangeable (the C-52 has provisions for mounting the starter on either side of the engine), but the SC used the E-51 (pretty much the same internals as the 91 Turbo tranny IIRC). If you put in the E-51 transmission with an SC motor into an 85/86, you will have to modify some of the mounts and get longer shifter cables and a different set of axles (cables and axles for any NA). If you aren’t planning on making big power with an SC motor, you can use the C-50 or C-52 that is already in your car with the stock flywheel from your NA, and save yourself a lot of headaches. You’ll just spend less time in each gear (1st will fly by like there’s no tomorrow) with the extra power. because the NA transmission has shorter gear ratios than the SC. It really is a lot easier/cheaper to stuff in a stock SC and put on a bigger pulley, than try to make big power with the NA. With the SC, you crank up the power with more boost without really affecting drivability, but to make power with the NA means you’ll lose some bottom end and drivability.

Header - don’t mess with it. The stock header should only be replaced if you’re putting in some mean cams, or if yours is cracked. Testing has been done, and the stock header is rather good. It will flow just fine. The $350 it will cost for one could be put to way better use somewhere else. I think only maybe 1 or 2 companies even make a header for the AW11 - I’ve never really looked to see who is still making them. You might consider a different exhaust (pull the cat too) but not for flow - only for the weight saved. I’ve used a couple different exhausts and the only thing that made a difference was one of them was messed up and was choked to about 1 1/2" after the cat in an attempt to get it to pass CA smog. Anything over 6k felt like crap. Other than that, they all feel the same to me. You will get a little more zing in the top end (maybe 4 or 5 hp if that) by getting rid of the stock intake system, and just mounting a filter directly to the AFM (there are writeups, and I’m working on a sturdy rally-grade kit) and the AFM to the throttle body.

The biggest gain you will get with these cars is in the suspension. Always Always Always upgrade the suspension before going for big power. Get some Tokico, or Koni adjustable shocks, Eibach pro-kit or ST springs, the High&Tight/Prothane bushings, High&Tight rear swaybar (or if you like oversteer mess around with a new set of front end links, and a '92 turbo rear sway - you can also get the suspension techniques front and rear sway kit), a front strut bar, better brake pads (Porterfield R4S, Hawk HPS) and new rotors, stainless brake lines and clutch line, short shift kit, and get some decent rubber on it. I like light 15" wheels, with 205 width sticky tires. I have 16"s on mine, and there’s just not enough feel to them. The sidewall is too stiff and too hard to tell when you’re pushing past the envelope. Also, consider a smaller steering wheel like a Momo (11.8" in mine). Also, Lotek makes a gauge pod which covers part of the A-pillar. Not too bad of a piece, but watch out when you’re installing it that you don’t drill through any of the rubber drain tubes in the body a-pillar (assuming it’s a sunroof). Check out www.twosrus.com as they have a lot of this stuff for decent prices.

I know Eibach for a short while wasn’t making our springs, but they have released a new batch. The TRDs, if you can find them, are supposed to be a bit stiffer, but I think the Eibachs are pretty darn good and do the job well. Some people kinda hack a Miata coilover set to make them work, but it worries me that at full unload, there is a gap between the spring and perch. I would really prefer a coilover kit that is designed for this car and fits correctly (only because my car does occasionally see airtime - blown a few cheap struts too but no springs… like I said, I like the Eibachs).

You could also consider a lightened flywheel. They improve the on and off throttle response of the 4ag a lot. If you plan on going with a GZE, get a GZE one, as it will handle the torque and your clutch will last longer. Also, if you go with a GTE, look at a megasquirt running the megasquirt-n-spark extra firmware. I have a writeup from JamesL, which is available here, as to how to make it work with the stock wiring harness, and stock ignition system.

Also, upgrading the ECU won’t really do anything for you with a stock 20v or 16v motor. Changing fuel and ignition timing may gain 1hp or so, not enough to notice, or make the cost worth it. The only reason to go to a standalone is if you’re going to turbo or sc the car (and it wasn’t turbo or SC already), or are going to spend the huge amount of money it costs to make NA power with cams and other head and bottom end modifications. Toyota really did tap most of the available power out of these motors.

TedComponents - http://www.tedcomponents.com/4ag.htm - can make you an awesome head and cam setup, and even a full motor, but it costs a pretty penny, and will not net you a whole lot unless you want to sacrifice all your bottom end for more top end. The best way to make more power (after you get all your suspension fixed up) is to do a GZE swap and either put on a bigger pulley (NonStopTuning - http://www.nonstoptuning.com/NSTPULLEYS/pKitToyMR2GZE.html) or make it turbo. You get the bottom end grunt and the top end scream. The 20v is fun for people who can keep it on the redline all the time, but for a car that you’re going to drive a lot, or want more than 170 horsepower, the GZE/GTE is a better option.

A final thing to consider is a 3SGTE swap from a 2nd gen turbo. It’s a huge amount of work with both fabrication, and wiring. You’ll get better oomph from the 2L motor, and can make more power than the 4AGTE or 4AGZE, but it’s a lot heavier, and a lot of work.

I guess then it would be better to just get a car that came with the supercharger… but as far as I’ve heard the later MKIs were heavier and handle worse… is there any truth to that? and is there a twin charge kit available for the 20v? or the 16v? that always seemed like a nice option, not just running both but having bypass valves and stuff…

They re-designed the later model mk1s to a suspension that was “more predictable, and safer for the inexperienced driver” (or something similar). In other words, they used bigger struts and removed the rear sway (except on SCs). There were some other changes in suspension such (there were a lot more than these though overall) as slightly different hubs, bigger brakes, etc. The only advantage I can see is the larger brakes, though as far as I know, no one has tested to see if they actually stop better. The later models are also a bit heavier, but not much. The SC is a couple hundred pounds more than the NA.

There is no twin charge kit ever produced (as far as I know) for a 20v, as the twin charge kit was only designed to go on the SC. They are extremely hard to find (last I heard Ken Tokowitz had two of the manifolds and some electronics, but it’s been years since I talked to him). HKS also made just straight turbo kits for the NA with bigger injectors, and a piggyback F-Con fuel controller, but good luck finding one. They’re almost as rare as the twin charge (watch out, some people on e-bay like to try and sell their AE86 HKS turbo manifolds (which aren’t too rare) as AW11, but they don’t fit without re-working the engine compartment. Twincharger setups are pretty crazy too. I agree… trying to run all the bypass valves and whatnot is a pain without the original purpose-built HKS electronics and hardware.