Lucifer Posted September 10, 2006 Share Posted September 10, 2006 hi guys. we have a car that produced 251bhp the other day. we are also just finishing out street na with headers, exhaust, single plenum intake, aem ecu, cams and a few other trick bits and are hoping for 270. 350 is acheivable on this engine, but very expensive, we are going down the throttle body route after doing a stage 1,2,3,4 for the na giving from 230-300bhp. should have the na on the rollers next week, so well keep you posted. Quote Link to comment Share on other sites More sharing options...
cookci Posted September 10, 2006 Share Posted September 10, 2006 are those figures at the fly? Quote Link to comment Share on other sites More sharing options...
Digsy Posted September 11, 2006 Share Posted September 11, 2006 Right-ho. First off, you aren't going to get much above 13 bar BMEP on an NA engine using off the shelf stuff. Let's say 13.5 absolute maximum. That's just about the current limit of getting air into the cylinder of its own accord (i.e. without using forced induction). The Supra is a 3 litre lump, and torque = BMEP x volume / 0.12556 to working out your torque for a given BMEP is simple maths. Also, power (simply put) = torque x engine speed, so it follows that for any engine you can work out the peak power if you know the engine size and the BMEP at any given engine speed (or, the BMEP curve). Sine all you crazy boy racers are interested in is peak power figures, you can simplify this even further to saying you can work out what your peak power will be if you know the peak power speed and the peak BMEP, but this is where the problem comes in. I have already said that you can't get above 13.5bar BMEP. For now, lets assume that the Supra won't rev past 6800 RPM. Assuming you can make the peak BMEP conincide with the peak engine speed, then the most power you can make in this configuration is 308bhp at the flywheel. The trick achieving this in real life is to make the peak BMEP occur at the peak engine speed. In reality this means that you have to tune everything: intake runners, exhaust headers, cam profiles and timing, etc, etc to all come on song together at this one engine speed. Once you have done that, then the only way to shoot for higher power is to either increase the engine size, or increase the engine speed, or both. So, let's adopt the VVTi max speed of 7200RPM and bung in a stroker kit for 3.4 litres. Re-tune everything again to move the peak BMEP (which will still only be 13.5bar) to the new max speed and you get 370bhp, which is a pretty fecking impressive figure for an NA in anyone's book (123hp/litre). Now, here's the rub. I mentioned earlier that this was assuming all you are interested in is peak power figures. If you made this engine, and if it worked like it said on the tin, then it would be so optimised for high power that the torque curve would be shitty and it would feel dead as a doornail to drive at low engine speeds. This is why modern engines use technologies like variable length intakes, variable cam timing, and cam switching. These systems effectively move the peak BMEP up and down the engine speed range so that is you are tooling around town you can have a car with 13.5 bar BMEP at 4000 RPM, but when you are blatting down the autobahn you can have it up at 7000RPM. But, you can't have both at the same time! So i'd say 300 ish by just optimising cams, intake and exhaust, 320 by upping the revs, 350 by stroking it and 370 by doing both. Quote Link to comment Share on other sites More sharing options...
Wez Posted September 11, 2006 Share Posted September 11, 2006 Great post Digsy Quote Link to comment Share on other sites More sharing options...
Daston Posted September 11, 2006 Share Posted September 11, 2006 Well said Digsy this is the reason why I am interested in Max touque as early as possible as the drivability should be a lot better Quote Link to comment Share on other sites More sharing options...
boombastictiger Posted September 11, 2006 Author Share Posted September 11, 2006 So i'd say 300 ish by just optimising cams, intake and exhaust, 320 by upping the revs, 350 by stroking it and 370 by doing both. What do you think a realistic parts and fitting price would be for this? Quote Link to comment Share on other sites More sharing options...
Lucifer Posted September 11, 2006 Share Posted September 11, 2006 Our 270 package is £2000 Fitted. Quote Link to comment Share on other sites More sharing options...
Digsy Posted September 11, 2006 Share Posted September 11, 2006 What do you think a realistic parts and fitting price would be for this? Well, Lucifer's given you a price for his kit to get you to 270. Not sure what's included, but I'm guessing cams, intake and exhaust - and unless I'm mistaken they'll be off the shelf parts. Maybe Lucifer can clarify. If you want to shoot for proper big power in an NA then IMHO you are really talking about bespoke parts, though, and then you are talking megabucks because as I said its all got to be single-mindedly aimed at hitting that magic BMEP number at your desired peak power speed. TBH, 13.5bar is state of the art - everything turned up to 11. There's a lot more engines hovering around the 12.5 / 13 mark. Without a proper development budget behind you (some simulation, a variable length intake stack and several shots at the best cam profiles) I don't think anyone stands a hope in hell of hitting it using off the shelf parts. You could maybe add a zero to Lucifer's 270 £2000 kit just to develop the intake, exhaust and cams - and then you have to go out and buy the stroker kit and ECU to get it up to 3.4litres at 7200RPM. Quote Link to comment Share on other sites More sharing options...
MONKEYmark Posted September 11, 2006 Share Posted September 11, 2006 this looks great,its turbo n/a but look at this car.read the supra forums thread if you a member 2jzge powered Probe 9.15 @ 148!!!! thread on supra forums http://www.supraforums.com/forum/showthread.php?t=376325 http://www.boostwerx.com/Matt/5-20-06B.JPG Quote Link to comment Share on other sites More sharing options...
bromy Posted September 12, 2006 Share Posted September 12, 2006 Yes it's another of dave henry's monsters, he did a 9.5 sec na-t supra too using stock internals Quote Link to comment Share on other sites More sharing options...
Thorin Posted September 12, 2006 Share Posted September 12, 2006 Is that some kind of low-profile dizzy? It's another option rather than mounting it directly on the cam gear if you want extra space. Quote Link to comment Share on other sites More sharing options...
jim_supra Posted September 12, 2006 Share Posted September 12, 2006 Is that some kind of low-profile dizzy? It's another option rather than mounting it directly on the cam gear if you want extra space. No, it looks like he's converted to coil packs, but you can't remove the dizzy completely on an NA when you do this, so he's just taken the cap off. Quote Link to comment Share on other sites More sharing options...
Thorin Posted September 12, 2006 Share Posted September 12, 2006 No, it looks like he's converted to coil packs, but you can't remove the dizzy completely on an NA when you do this, so he's just taken the cap off. Ah yes, didn't look too closely. I still wonder why that Venom Supra still uses a dizzy and didn't convert to coil packs. Quote Link to comment Share on other sites More sharing options...
dangerous brain Posted September 12, 2006 Share Posted September 12, 2006 Yup I'd like to see a built NA engine with individual throttle bodies... Time to put my lottery numbers on MK3 board has a set of 6 throttle bodies for sale if thas any help http://www.forum.mkiiisupra.net/showthread.php?t=13979&page=3&pp=15&highlight=throttle+bodies Oh too late but you might ask nod where they came from. Without forcing the induction the 2JZ is very expensive to squeeze power out of it. Lol at novotel its a hotel chain in holland Isn't BMW's variable valve system called VANOS ? Quote Link to comment Share on other sites More sharing options...
boombastictiger Posted September 12, 2006 Author Share Posted September 12, 2006 what are throttle bodies? and stoke kits? Quote Link to comment Share on other sites More sharing options...
dangerous brain Posted September 12, 2006 Share Posted September 12, 2006 Throttle bodies are the big metal section just over the top of your cylinder that effectively feed the air into the valve area of your engine. Its where the butterfly valve is that opens and closes which allows the air in basically. A stroker kit is a piston/cylinder bore kit that effectively increases the displacement of your engine ie makes a 3.0 litre engine into a 3.2 or 3.4 litre engine. A stroker is also someone that has a tendency to play with themselves too much as well Quote Link to comment Share on other sites More sharing options...
Digsy Posted September 12, 2006 Share Posted September 12, 2006 A stroker kit is a piston/cylinder bore kit that effectively increases the displacement of your engine ie makes a 3.0 litre engine into a 3.2 or 3.4 litre engine. A stroker kit won't have anything to do with the cylinder bore (I'd like to see a cylinder bore kit, though ) It will consist of a new crank with a longer throw (the distance between the main bearing centreline and the crankpin centreline) and either shorter rods or new pistons with a decreased crown height (so that the assembled length of the crank, rod and piston is the same as stock). The purpose of a stroker kit is to increase the engine's zise by increasing the stroke - the distance by which the piston moves up and down in the bore. Quote Link to comment Share on other sites More sharing options...
Digsy Posted September 12, 2006 Share Posted September 12, 2006 what are throttle bodies? and stoke kits? You're the guy doing the automotive degree aren't you? Not being funny and I don't want to start a slanging match but I would recommend that you buy yourself a decent reference book and sit down and have a read. Just a friendly suggestion. Quote Link to comment Share on other sites More sharing options...
Thorin Posted September 12, 2006 Share Posted September 12, 2006 I'd like to see a cylinder bore kit, though Walls are too thin really, it's practically the 2.5 1JZ bored out to 3.0 already. Quote Link to comment Share on other sites More sharing options...
Kranz Posted September 12, 2006 Share Posted September 12, 2006 A cylinder bore kit would be better than a stroker kit as it would not lower the safe operating speed of the engine, which would be needed if increasing the stroke length. Increasing the stroke increases the forces on the crank pin, rods & pistons, but reduces the friction. Increasing the bore diameter keeps the forces on the pistons & rods about the same, but increases the friction due to more piston ring circumference against the bore wall. But if you go for a fully counterbalanced billet steel crank, H beam rods & lightweight forged pistons and this lower RPM limit can be forgotten. To get the most from an NA you need to make the air inlet & exhaust as unrestrictive as possible, and squeeze the heck out of the contents of the combustion chamber with the most advanced ignition timing possible. This would be helped by running on the highest octane fuel available and using an aggressive knock control system that keeps the advance right on the det limit (DBL-1). Things like dry sumping and engine blueprinting make quite a difference but then you're into ££££ territory. Why not just get a TT?? Quote Link to comment Share on other sites More sharing options...
Digsy Posted September 12, 2006 Share Posted September 12, 2006 Walls are too thin really, it's practically the 2.5 1JZ bored out to 3.0 already. I was thinking more in terms of a kit of bolt-on bigger cylinder bores. Kind of like a bag of skyhooks or a metric adjustable spanner or a jar of elbow grease... Quote Link to comment Share on other sites More sharing options...
Digsy Posted September 12, 2006 Share Posted September 12, 2006 A cylinder bore kit would be better than a stroker kit as it would not lower the safe operating speed of the engine, which would be needed if increasing the stroke length. Increasing the stroke increases the forces on the crank pin, rods & pistons, but reduces the friction. Increasing the bore diameter keeps the forces on the pistons & rods about the same, but increases the friction due to more piston ring circumference against the bore wall. But if you go for a fully counterbalanced billet steel crank, H beam rods & lightweight forged pistons and this lower RPM limit can be forgotten. Good point. Going from 3.0 to 3.4 would put the rod inertia loads up by about 15% at TDC, which would severely limit you in subsequently upping the rev limit. I did say it would be difficult... Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted September 12, 2006 Share Posted September 12, 2006 OS Giken do a 3 litre wet liner big bore kit for the Skyline RB26 engine, and no doubt something similar COULD be done for the Supra, given enough money. http://www.osgiken.co.uk/3litrekit.asp It's expensive and not to my liking, but it seems to work well Quote Link to comment Share on other sites More sharing options...
garethr Posted September 15, 2006 Share Posted September 15, 2006 The throttle body is the thing which is connected by cable to the accelerator pedal. Individual throttle bodies (ITBs) -- one throttle body per cylinder, rather than one throttle body for all 6. The cheap(er) way to ITBs is 1.5 wrecked superbikes (or 2 if they are Triumphs). Then you need manifolds and an ECU. Edit: I answer the phone and 95 people post Quote Link to comment Share on other sites More sharing options...
boombastictiger Posted September 15, 2006 Author Share Posted September 15, 2006 so if the standard NA engine was upgraded to say 300hp, and upped to 3.4l, would it be able to take on a turbo charger/supercharger on top of that? Quote Link to comment Share on other sites More sharing options...
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