Increasing torque with out forced induction

[aesthetect]

Originally Posted by W204

Nice to see a fellow w204 owner here

If the 2.5RS is any indication of boxer NA engine tuning, it is going to be tough. There are very few EJ251's(zzyzx for example) running at 300whp NA and it had such a wide array of parts such as racing cams, ported and polished heads, throttle body, and intake manifold, racing pistons, lightened crankshafts, lightened rods, etc.

I'm guessing the FA20 will probably top off somewhere between 240-250whp with general mods such I/H/E/T and that's just well wishing. That's exactly fine with me as that's perfectly where I would want my 86 to be in.

actually there are zero ej251s running 300whp out there. to be perfectly honest the zzyxx claims are overstated, anyone with a NA EJ25X can tell you youll barely break the 200chp mark with all that and high compression internals (there are plenty of builds out there with teh same setupas zzyxx which fall into this category).

although i concede it bears minimal semblance to the FA20, its closer than anything else out there, so to keep with discussing the EJ251: cams are the only thing that really got any power out of it. stock intake is hardly restrictive, you maybe get some pep out of a set of headers, but nothing substantial.

if torque is the goal, what i would be interested in is increasing the intake manifold runner length. although i believe there was something said to the effect of they had to compromise on this for fitment, if its that close maybe there is some sound deadening in the hood that can be removed, maybe some spacers can be inserted.

better option: i also recall hearing some discussion from the FHI engineers that some slightly stiffer valve springs are all that really stand between teh FA and a higher rpm redline. thus id say change the cam profile for higher rpms and put in some stiffer springs and youll get some power.

the question to me with all this is re-tuning the D4S system. it will certainly be a pain in the ass for tuners to reverse engineer the control algorithms. but from what ive heard from teh guys at cobb, the potential is great. how much of a tune would be necessary for a cam/valvespring build like i mentioned? how much room is there for the stock engine to grow from a retune? is everybody gonna just start abandoning the direct injection system?

[serialk11r]

Originally Posted by aesthetect

the question to me with all this is re-tuning the D4S system. it will certainly be a pain in the ass for tuners to reverse engineer the control algorithms. but from what ive heard from teh guys at cobb, the potential is great. how much of a tune would be necessary for a cam/valvespring build like i mentioned? how much room is there for the stock engine to grow from a retune? is everybody gonna just start abandoning the direct injection system?

We have yet to see how easy it is to access the ECU, but the press rumors say it shouldn't be too hard (but rumors are rumors). 3MI Racing I think is working on the trickier things like pistons and high pressure injector replacements.

At this point not many people know how much more rpm the engine can take, or how much boost it can take, but we have a few clues. The relatively low torque and apparent compromise made for increased low rpm driveability suggest aiming for higher rpm torque with the intake headers and cams could yield good results. Seeing how the 3S-GE with TRD cams and various upgrades made more specific torque than the Ferrari 458, despite an older design, things could be promising.

[Dimman]

Originally Posted by serialk11r

We have yet to see how easy it is to access the ECU, but the press rumors say it shouldn't be too hard (but rumors are rumors). 3MI Racing I think is working on the trickier things like pistons and high pressure injector replacements.

At this point not many people know how much more rpm the engine can take, or how much boost it can take, but we have a few clues. The relatively low torque and apparent compromise made for increased low rpm driveability suggest aiming for higher rpm torque with the intake headers and cams could yield good results. Seeing how the 3S-GE with TRD cams and various upgrades made more specific torque than the Ferrari 458, despite an older design, things could be promising.

The thing about the TRD motor is that when people say they want 'torque', what they really mean is 'low rpm torque' and giving them that while keeping the higher rpm torque (power) is tough. This is where all the variable geometry intake systems like Toyota's dual runner TVIS (inertial) and multi-length ACIS (acoustic) systems (and exhaust like EXUP on bikes) came in, as well as the assorted variable lift systems. They all are trying to 'double tune' the motors for low and high rpm. And that is probably way beyond what the aftermarket can do because of cost/complexity.

We will only have the cam phasing to play with.

[serialk11r]

Torque is torque, not lack of high rpm torque :P

I know the title of the thread says "without forced induction" but a Roots supercharger would take care of that low rpm torque issue hehe.

Personally, I'm getting excited about the idea of lower volumetric efficiency at low speed, because that reduces part load pumping loss hehe.

[Calum]

Originally Posted by Daemione

Of course you can do both. But I have to question to the efficacy of it . . . and any sane person will look very hard at the value, considering the cost of that kind of modification.


This is what jumped out at me. Again . . . yikes.

Removing the transmission, separating the bellhousing, removing the shafts and taking them to a shop to have the gear pressed off and a new one pressed on isn't that big of a deal to everyone. Especially if the car isn't required as a DD.

As for efficiency, if you match the rear end gears and sixth gear correctly, you're highway cruising rpm wont have changed much. That means you're highway cruising efficiency wont have changed much but you can get the benefit of a higher (numerically) final drive ratio.

[civicdrivr]

Originally Posted by Calum

As for efficiency, if you match the rear end gears and sixth gear correctly, you're highway cruising rpm wont have changed much. That means you're highway cruising efficiency wont have changed much but you can get the benefit of a higher (numerically) final drive ratio.

This is what I'd like to do. That way the 1-5 gears are shorter but 6th isn't changed from stock - as far as revs go.

[aesthetect]

Originally Posted by serialk11r

We have yet to see how easy it is to access the ECU, but the press rumors say it shouldn't be too hard (but rumors are rumors). 3MI Racing I think is working on the trickier things like pistons and high pressure injector replacements.

At this point not many people know how much more rpm the engine can take, or how much boost it can take, but we have a few clues. The relatively low torque and apparent compromise made for increased low rpm driveability suggest aiming for higher rpm torque with the intake headers and cams could yield good results. Seeing how the 3S-GE with TRD cams and various upgrades made more specific torque than the Ferrari 458, despite an older design, things could be promising.

haha yes those were meant to be rhetorical questions.

but yeah thats why i mentioned the valvesprings/rpm, its one of the only 'tidbits' ive heard, and apparently straight from one of the FHI brz engineers, although it still needs to be taken with a grain of salt obviously.

i fail to see how a compromise of torque output would be done to improve driveability? but yeah, several reviews have noted it seems happy at high rpms, which is definitley not the case for a stock ej251. 3s-ge is obviously different in a lot of ways...

[Dimman]

Originally Posted by aesthetect

haha yes those were meant to be rhetorical questions.

but yeah thats why i mentioned the valvesprings/rpm, its one of the only 'tidbits' ive heard, and apparently straight from one of the FHI brz engineers, although it still needs to be taken with a grain of salt obviously.

i fail to see how a compromise of torque output would be done to improve driveability? but yeah, several reviews have noted it seems happy at high rpms, which is definitley not the case for a stock ej251. 3s-ge is obviously different in a lot of ways...

3SGE is a better reference given the same bore and stroke, as well as dual cam phasing. Issue with the EJ25 at high rpm is the shitty combustion from its larger bore which will get worse with compression increases. Also for the fact that Toyota kindly pointed out to Subaru that getting enough valve into an 84mm bore for 200hp of airflow might be a nuissance.

The compromise comes from what people are calling the torque 'dip'. Given the bore size and intake valve estimates based on it (34.5mm?), intake velocity should put peak torque at ~4800-5000 rpm, like the automatic-tuned BEAMS 3S. Instead it is crawling out of a bit of a low point around there. This is similar to sportbikes that are tuned for multiple acoustic return values. They end up with two scavenging boosts from the acoustics, but are left with a 'flat spot' in the rpm between them. The cam phasing can somewhat enhance the good and minimize the bad. Plus if the bad acoustic return is tuned to near the optimum intake velocity range they can end up with a very flat torque curve.

[Daemione]

Originally Posted by serialk11r

By the way, the people who you've heard of switching out their top gear, are their experiences posted on the internet? I'm curious because I've only ever seen (on the internet) 1 person do it.

Yup, it's not common at all. It's a huge pain in the ass, and even between transmissions that should have compatible/swappable gearsets, there's no guarantee that's the case until you're elbow deep into the project. Then when it's all said and done, there's so little payoff that it isn't worth it. An extra 3-500 rpm difference at highway speeds just doesn't make a measurable difference.

The only ones I know of off hand are a few people with Preludes who swapped out the 5th gear cog for the Accord's. Although it makes more sense to me to just use the F22 transmission with a custom final drive gear vs. the lazy stock one. I'm remembering discussion of it on Honda-tech.com? But it's been a long time.

[Daemione]

Originally Posted by Calum

Removing the transmission, separating the bellhousing, removing the shafts and taking them to a shop to have the gear pressed off and a new one pressed on isn't that big of a deal to everyone. Especially if the car isn't required as a DD.

[serialk11r]

Originally Posted by Daemione

Yup, it's not common at all. It's a huge pain in the ass, and even between transmissions that should have compatible/swappable gearsets, there's no guarantee that's the case until you're elbow deep into the project. Then when it's all said and done, there's so little payoff that it isn't worth it. An extra 3-500 rpm difference at highway speeds just doesn't make a measurable difference.

The only ones I know of off hand are a few people with Preludes who swapped out the 5th gear cog for the Accord's. Although it makes more sense to me to just use the F22 transmission with a custom final drive gear vs. the lazy stock one. I'm remembering discussion of it on Honda-tech.com? But it's been a long time.

Yea, I imagine it is typically quite difficult, but the fuel economy gain is definitely measurable...besides, it's the ratio, not the absolute difference in engine speed, that matters. It obviously depends on how much you drive and what kind of roads you drive that will determine whether or not it's "worth it" (along with how much you can change the gear ratio).

[aesthetect]

Originally Posted by Dimman

The compromise comes from what people are calling the torque 'dip'. Given the bore size and intake valve estimates based on it (34.5mm?), intake velocity should put peak torque at ~4800-5000 rpm, like the automatic-tuned BEAMS 3S. Instead it is crawling out of a bit of a low point around there. This is similar to sportbikes that are tuned for multiple acoustic return values. They end up with two scavenging boosts from the acoustics, but are left with a 'flat spot' in the rpm between them. The cam phasing can somewhat enhance the good and minimize the bad. Plus if the bad acoustic return is tuned to near the optimum intake velocity range they can end up with a very flat torque curve.

im not following you as far as what on the FA correlates to multiple acoustic resonance ponits (being something i would attribute to fixed manifold geometries etc)... i think youre saying the bore and intake valve size are such that theyd typically be making peak torque at 4800-5000 rpm, but the manifolds/cams/etc are tuned for lower rpm, which is what results in a relatively flat torque curve?

vivid racing's dyno seems to fully corroborate what you are saying

Originally Posted by Daemione

Yup, it's not common at all. It's a huge pain in the ass

agree i dont see how splitting a trans case to replace 1 gear cog is anything short of a giant pain in the ass. particularly compared to just changing the final drive out of a rear diff.

[Circuit Motorsports]

Realistically, for most people the best route will be Intake, Headers, Exhaust, Tune for highest octane available in your area, enjoy

Past that you're going to be getting into a lot more money and work. The sky is the limit, how deep are your pockets?