i was looking through the last subiesport not that long ago and they had a speal on the 07 WRC car. the specs which caught my eye, were the Hp and TQ #s. They stated that the car had 300HP, and 400+ft/lbs TQ! now i know that Hp is heavily regulated in the WRC and 300 is the limit. it also seems right that they can have whatever tq they want. my question is, how do they get 400ft/lbs and have the hp stay right at 300. that is a huge difference. any clues?
I don't follow much on WRC, but if it is using the 2.0L It is hard to imagine 400tq coming out of it...
Even if u change out all the manifolds and increase the diameter of all your airflow, it's hard to see how your TQ is 100+more than your HP rating...I'm sure it is all in the tune as well...
A 2.0L can easily make 400tq. Remember, the heads are probably worked over like crazy. Lots of flow. Very little intake piping on a large intercooler. The turbo is a custom IHI piece, not some run of the mill VF turbo. Race gas. There are a million things that are different between your street variety passenger car, and a purpose built rally car.
I don't see how that is the case, have you seen the dyno plots for this setup? Also, have you ever heard of a semi-truck? Those things have gobs and gobs of torque but not much in the way of horsepower. Bob, a member of this club, has an 06 WRX with a turboback exhaust. He made 195whp, 225ft/lbs torque. It is entirely possible, and normal.
I guess I'm thinking more in our Street Car mentality/mods...I can see Bob getting the higher TQ #'s due to the fact it is a 2.5L as compared to a 2.0L and proper tuning...I know it is possible to get 400tq out of a 2.0L heck I think I'm around 340tq with a vf34 so I know it is possible, but with higher tq I'm just use to seeing higher HP as well...being 100+ difference is more like SUV #'s...
Well, you need to remember that they use restrictors, so the overall cfm through the motor is limited. What they do to compensate for the lack of volume is use alot of boost. Crazy amounts of boost (think turbo deisel). Russ
Oh ya, and if you were to look at a dyno graph of the power it is all low end stuff. Those motors don't do so hot over 6500 rpm. Russ
when i was on my stock t25 with the sr20det, i was making a lot more tq than hp (can't find the stupid dyno graphs on this comp).
I'll try to make this as understandable as possible (cause i still draw a blank at some points): WRC is 2.0l restricted, but stroke is not and boring is legal within tolerance. The displacement is not the limiting factor though: all WRC cars are required to run a restrcitor plate that limits the intake openning to 37mm. There is no horsepower "limit" only the limits of the air intake system. So the big question: how do they get that torque without the HP? Simple answer: shift powerband lower by: cams, cam timing, small turbo for quick spool but less air, then advance timing as far as possible. WRC engines have knock thresholds like you wouldn'y believe. torque is all about cramming air into the cylinder, combustion pressure,which happens very early in WRC, Hp is all about how well your engine gets air, this is restricted. So HP is limited not to a number, but because the restrictor plates would give new meaning to the word Turbo-lag So WRC tunning moves sets a rev limiter just past the point of torque/hp cross giving you the peak torque numbers, and making you shift before reaching a theoretical HP max number. It's not that the engine couldn't make more HP, but that the TQ is more important to keep the car resposive Summary: advance timing, build enigne to withstand any amount of boost, cut rpms before you get out of torque power band and into Peak HP
i was just going to say while reading this tread that i read somewhere that the only was to do that is to change the bore and stroke(longer) but keep the 2.0 displacement, Advance the timing as far as all hardware will be willing to go, and tune the built motor with a small fast spoolin turbo. I think it was SportCompactCar i could be wrong. But i got to Methodless post and he pretty much explained what i was going to say. Good ups
Small nits: WRC turbo inlet restrictors are 34mm The engines are also very high compression (for turbo engines) It's not a "restrictor plate" ala NASCAR, but a turbo inlet restrictor. Generally they are designed more like a velocity stack than a simple plate with a hole in it. Essentially, a restrictor works because air flowing through it cannot move faster than the speed of sound. That means for a fixed restrictor size, you have a finite amount of air that can be drawn through it. A finite amount of air means a finite amount of HP, the theoretical limit of a 34mm restrictor is somewhere in the neighborhood of 350hp (don't recall exactly), but that's in an ideal world, where your A/F was at stoich, and that's just not gonna happen becaue even built like they are, WRC engines would go boom real fast at 14.7:1. So 300hp is the generally accepted neighborhood that WRC cars get. So everything is geared towards producing as much torque down low as possible, because the engine just can't breathe at high RPMs.
The simple answer as some have already said is boost. Some of the WRC cars are making over 30 lbs of boost at 2000 rpm. My Group N WRX had the required 32 mm inlet restrictor and we made 24 lbs of boost at 2600 rpm with a stock turbo. However, the boost had dropped to 10 lbs at 5500 rpm due to the restrictor. The above is the reason that the right, close ratio gears are the key to making a rally car fast. The car may top out at 105 mph but it gets there in a hell of a hurry.
Since the restrictor allows a finite amount of air into the engine, hitting that limit as early as possible is in their best interest. The heads and all associated harware are prob desinged to flow the best in that early range to take advantage of it, therefore high torque #'s. Look at my heads. They are designed with low to midrange torque in mind. When my turbo hits around 3800rpm its pretty wild, but peters out by 6k. I should end up with significantly higher torque than hp, but its all happening lower in the rev range. My heads are a restrictor in a way. A GT35R with these heads would be a waste since I cannot take advantage of it up top. The heads are just too restrictive.
ahh i see. couple follow up questions. wouldnt pushing 24psi out of a stock turbo be out of the efficency range? and how do you build boost so fast? anti-lag? What type of gearing are they running? are we talking short like the V6 STis (4.44 FD) or shorter? what would happen if you took the restrictor out of a wrc car? would it still have gobs of low end tq, would it gain excessive hp in the high end?
I'm pretty shure the turbo is very far from stock. Extreme custom units from IHI. Turbos that can hold up to antilag start at around $4500 IIRC. They would have to be designed to spool when they when they want in the rev range, which is also dependant on their gearing. No restrictor would goof up their whole arcitecture. The motors are built around that restrictor. If it were opened up, everything would have to be changed. Cams, porting, turbo, tuning, gearing, and what not. When I was involved with the Formula SAE car in Duluth, we had to completely redesign the intake manifold for the 20mm restrictor on a 600cc bike motor. If that same manifold was used without a restrictor, the motor would have been a turd. A lot of desing goes into where you want the flow to be the best, with respect to runner length and plenum size. When tuning an intake on an NA car, you can design in almost 10psi of pressure at the valve when it opens. But how peaky do you want the power band? All in all, its a very delicate balancing act.
And didn't most of that come about with the dissolution of the Group B cars? The top speeds that could be reached with unlimited HP numbers (as opposed to the monsterous torque) on some rallies, such as the Safari Rally, are too dangerous even for rally drivers as good as the WRC guys. Part of that was to make things just a little more safe for everyone involved. For those that haven't watched a WRC event you really need to check it out. Watching it on TV is educational enough but you can also volunteer to crew for local rally teams and learn just a ton about our cars, even if you do consider yourself pretty knowledgeable. And some of those rally crew chiefs come up with some genius ways to repair things on the fly in a hurry.
wait a sec here. they make turbos that can withstand the constant pounding of anti-lag?!?! i did not think it was possible. ALS...........FTW!
yes, the anti-lag helps with this power maker, especially the torque curve when you open the throttle.
