|Ideas expressed here are my opinion and should be taken as such. I take no responsibility for the accuracy of information on this page although I try to be as factual as possible. Please research before you make modifications to your car and get information from multiple sources if you can. What you do to your car is your own responsibility.|
I've seen many threads lately about making power on the 5sfe and so I decided to add my 2 cents. Specifically concerning the idea of whether or not you can build a 5sfe powered car with 200rwhp. I believe you can and will expain why I think so and how it might be possible to do so.
Ok first let's look at this challenge logically. The formula for HP is: Torque * rpm / 5252. This gives us a basis for all our calculations and a way to equate real world modifications to our goal. If you look at any dyno chart you will see that an engine has an rpm range in which it performs the best as represented by the torque curve. The toque peak of an engine is where it is operating most efficiently (generally speaking, flowing the most air and fuel). So by using the formula above and doing the math we can see that the easiest way to get high HP numbers is to produce the most torque at the highest rpm possible. Make sense so far?
Now let's look at the 5sfe and it's stock characteristics. We need a basically stock dyno, I'm using this one because it was readily available: http://www.mr2ownersclub.com/mr2records/dyno/mgawlowski.jpg This is very characteristic of a 5sfe with stock cams as you can see the double torque peak at 3700 and 4300rpms and then a steep fall off starting around 5000rpms. Now let's compare that to the highest recorded HP NA 5sfe that we know about: http://www.mr2ownersclub.com/mr2records/dyno/jsnodgrass.jpg In this dyno Jim was using a 294 (244 advertised duration) intake cam but a stock exhaust cam. His torque peak is still happening at 4300rpms but something interesting to note is that the first peak is gone. I believe this is because the 294 cam flows best at around 4300rpms and matches up better to the stock exhaust cam, increasing the effectiveness. This might be a good argument for having a staggered cam setup in a 5sfe but that's another discussion. If you look really closely, other then that missing torque peak, these two engines have very similar curves but then again they are the same engine after all. So what makes them different?
The answer to that question is simple... flow and tuning. According to Jim's website his mods are:
"The motor currently outputs 147 STD rwhp/153 STD rwtq as compared to the @105 HP and @125 tq of a stock n/a MR2. This was accomplished with larger cams (Webcams 294 grind intake, stock exhaust). The head was also ported and polished and had a 5 angle valve job. There is a custom built 4-2-1 stepped tube race header exiting through a 2.5" straight pipe. A few other performance mods include a Crane performace coil, an Apexi intake, and Jacobs spark plug wires. This is all being controlled by an Accel DFI gen 7 stand alone engine management system."
The important ones to note are the intake cam, port and polish, 4-2-1 header, exhaust, intake and the biggest one the DFI stand alone. Jim produced his torque peak at 4300rpms with these mods but what if he would have been able to produce 150ft/lbs at 6300rpm, the safe limit of the rod bolts and valve train in the 5sfe? Obviously he would have needed more flow mods to achieve this such as more aggressive cams to shift the torque curve up, maybe a custom intake manifold and throttlebody and possibly larger valves because more rpms means more air has to flow through the engine. In this case about 47% more. Let's do the math: Torque 150 * 6300rpm / 5252 = 180rwhp. That's close but still not to our goal of 200rwhp. Still it reasonable to assume a 5sfe can do this. Heavily modded turboed 5sfes have hit over 500rwhp and and you need a lot of flow to achieve those numbers even with high boost. Also it's sister engine, the stock 3sge with no mods, can make 140ft/lbs at 6000rpms and the displacement advantage of the 5sfe with the right flow mods to go with it would put it in that range.
So now what? Basically you have a couple of choices, make your engine more efficient at 6300rpms or increase the redline and do air flow mods for high RPMs. You can increase efficiency with things like higher compression pistons or shaving the head, a race quality port and polish, larger valves, tuned headers, velocity stacks or individual throttle bodies. I imagine you could attain peak torque numbers of 160-170rwtq if you did things just right. The magic number in this case though is 167rwtq to give you 200rwhp at 6300rpms. The other way is a little bit easier to pull off but you will have less area under the curve. It just so happens, using the formula above, that if you can make 150rwtq at 7000rpms you will be right at 200rwhp. If you can hit 140rwtq/7500rpms or 131rwtq/8000rpms you will also have just reached 200rwhp.
So what is the recipe for a 200rwhp 5sfe? Well here is one way I think it could be done:
- Stand alone engine management with redline set above 7500rpms and lots of tuning
- 350cc or larger top feed injectors
- Larger throttle body (like a 3sgte or 4age throttlebody)
- Custom intake manifold (shorter runners and slightly larger in diameter would be my guess)
- 1mm or 2mm oversized valves with headwork to match
- Quality port and polish (not just going at the head with a dremel)
- Stronger valve springs for 7500+rpms
- 264 or 272 advertised duration cams with 8.5mm or better lift
- 4-1 header tuned for power at 7000ish rpms
- 2.5" free flowing exhaust
- Forged 5sfe or 3sgte rods
- 98+ 5sfe oil pump shimmed to keep oil flow and pressure at high rpms
Did I forget anything? I'm sure there are other ways to accomplish this but this to me seems like the most cost effective and direct approach. Also, believe it or not, the rest of the fuel system and most other stock components are safe for this hp range. The fuel pump can handle 235rwhp at stock pressure, the fuel rail is huge and the ignition system is already known to handle 200rwhp under boost. Just remember you are basically building a 5sfe that has to flow more air then a 3sgte does stock. I certainly believe it's possible but it's going to involve planning, money, hard work and freeing up every major flow restriction. Of course this motor would be a dyno queen and probably wouldn't be quite as fun to drive around town as one with a broader powerband but hey you could say you have the highest HP all motor 5sfe in the world. :)
If you would like to add anything or correct and information that is inaccurate or outdated please feel free to PM me on the board or send me email. You can find me on www.mr2oc.com or www.mr2.com.