How to build up your 5SFE, Taken from the mr2 forum Options

[hioctane]

NOTE: THIS IS FOR THE 5SFE MR2 MOTOR. I HAVE BEEN HANGING AROUND THE MR2 FORUMS FOR A WHILE AND THOUGHT THIS MIGHT BE HELPFUL.

source: http://www.mr2oc.com/showthread.php?s=&thr...30&pagenumber=1

The 5SFE motor in the Toyota MR2 makes about 100 bhp at the rear tires as delivered from the factory…plenty for a commuter car but lacking for horsepower junkies. Very few people in the USA have even seriously attempted to get more power from this engine which is surprising considering how many millions of Toyota Camrys, Celicas, Corollas, and MR2s there are out there on the roads here in the states.

The stock Toyota 5SFE motor has a bore of 87mm and a stroke of 91mm which means it can safely be revved to about 7,000 rpm before linear piston speed becomes critical even though the stock redline is about 6,400rpm. The stock motor’s cam timing and lift make the power peak around 5,000 rpm with peak torque in the 4,500 rpm range. Once again fine for a commuter car but lacking the real grunt I am looking for. The stock Compression ratio is about 9.5:1….low enough to run without complaint on 85 octane fuel. My car is a California model which mean in addition to the Exhaust Gas Recirculation (EGR) and Evaporative Emissions systems I have two catalysts on the exhaust system with the first being less than 12 direct inches from the exhaust valves….very poor for power production, very good for tight emissions standards. The Engine/Electronic Control Unit for the fuel injection is also specific to a California model car. All 5SFE motors also ventilate the crankcase through the inlet manifold which is far from ideal since most of the gas the being ventilated is previously burned blow bye that got past the stack of compression rings on each piston. Just like EGR, PCV gases will not add to the power production of the engine since they contain next to no oxygen or beneficially combustible hydrocarbons. The stock single throttle body has a 50-55mm throttle plate to feed all four cylinders through ridiculously long intake runners designed to benefit torque off the very bottom of the rev range. Most if not all Toyota 4 valve cylinder heads are either produced by Yamaha or at least partially engineered by Yamaha, a motorcycle company with an excellent history of producing very high specific outputs from very small displacement motors. My goal with this project is to make my Toyota commuter car motor into an automotive version of a Yamaha Sport bike power plant with no less bottom end than the stock car and way more power everywhere else.

With a goal like this all I am really doing is a backwards engineering project on the 5SFE. A typical Yamaha 4 cylinder sporting motorcycle has around 12:1 compression, 4 individual throttle bodies with bores of approximately 40mm each, a stainless steel header of either a 4:2:1 or 4:1 design, cams designed for the greatest benefit in the mid to upper third of the rpm range, next to no emission control equipment, ram air induction, a generous airbox with lots of volume to perform well across a broad range of conditions and a maximum linear piston speed of about 4,500 feet per minute.



This post has been edited by hioctane: Oct 5, 2004 - 1:16 AM

[hioctane]

The stock exhaust system has now found it’s way into the rubbish bin along with it’s array of catalysts and its cast iron heft has been replaced with a stainless steel 4:1 header and mid pipe from a North Carolina Company called SSAutochrome. Their URL is www.ssautochrome.com. I give the URL only due to the fact that finding anything in the way of production performance parts for this car and this motor is nearly impossible, especially in the USA. I paid less than $300 for this item and it took only a few days to arrive at my shop which is what I consider great service! I like to support those who support the sport, and in this case these guys deserve a big plug. The header and mid pipe eliminated both of the catalysts on my California model MR2 and has oxygen sensor bungs for both the primary and sub o2 sensors. I have not been on the dyno yet as I have a lot more mods to do but this pipe really does feel as though it is making about 15-20 bhp more than the stock system. At the same time the new header dropped about 35 pounds off of the car and every pound lost can be felt when accelerating. It took about 5 hours to install in a fully equipped shop and was mated for now to the stock silencer/muffler that my MR2 came with. To compliment the header I switched out the California spec factory ECU for a 49 state model. The sound is very aggressive even through the stock muffler…raspy and rude. It will in time be replaced with a straight through silencer that should be quieter while offering a still greater increase on flow and reduction in back pressure.



Also high on my list of simple mods was to disable the stock EGR, PCV and EVAP emissions equipment since I do not want anything other than air and fuel going through my motor….since those are the only two things required to make good power. Disabling the EGR system is easy enough, just remove the vacuum actuator from the flow through valve and plug it off…without vacuum it will not allow flow of already burnt junk to enter the motor. I have since bought a set of block off plates to permanently disable the EGR and remove all of its cumbersome plumbing on my new motor. They are available through eBay and username: garagerevolution who sells them for about $20 a set for stainless steel block off plates. I added a crankcase breather filter from K&N and eliminated the hose that previously fed the throttle body crankcase gases. A similar step was taken to remove the California spec evaporative emissions canister and plumbing. Several of these steps will cause the check engine light to come on in the passenger cabin of the car…if this bothers you then you will need to source a factory shop manual and then find resistance values for all effected sensors and add resistors to make the cars ECU think all this junk is still on the car and functional. Since I will be replacing the entire stock ECU and inlet manifold I have not taken this step at this time. I have not noted any change in running characteristics or fuel economy on my car but others who have done similar mods have said the fuel economy will suffer a bit. Disabling the EGR has resulted in extremely light detonation at low rpm high gear low load conditions, all of this will be fixed when the new motor is installed and the new EMS (engine management system) is installed and tuned on the Mustang Dyno at CCS Tuning here in the Austin, Texas area. Their URL is www.ccstuning.com .