In my pursuit of ways to put my digital rpm switch to work on off nitrous duty, a new idea has crossed my mind. Raising the redline.

Essentially the ecu works the rev limiter by cutting off fuel pressure once the redline is reached. there are several apparent redlines. about 5000 rpms under 12 mph per the esm. about 6800 rpms in first gear per the esm. about 6900 rpms in second gear per experience. about 7100 rpms in 3rd gear when paddle shifting per experience.

I am very confident I can wire three relays into the fuel pump power wire. one to 'detect' that the power has been shut off, a second to 'feed' power back to the pump, and a third hooked up to the rpm switch to only 'feed' power below a certain rpm (say 7500 rpms) and above a certain rpm (say 6500 rpms) the function of setting a mininum rpm limit is to make sure that power is not given to the fuel pump under the low speed rev limit and when the car is shut off.

I can probably make it work. Unless the ecu also stops cycling the injectors at redline too, I can't work around that.

But should I?

As you boost aficionados already know, centrifugal force is the true bane of engines. 2ATMs of boosted combustion still applies less pressure downwards on the piston than the sudden reversal of momentum that occurs each time the piston naturally reaches BDC and TDC at 6000 rpms. It is the single greatest force applied to the rotating assembly. It increases by the square of the proportion of the increase in r.p.m. So (7500/6800)^2 = 1.217 times or 21.7% more centrifugal force being applied to the rotating assembly, including the valvetrain.

21.7% 'sounds' within factory tolerances. However, is there even a fuel map above 7100 rpms? Will the ecu get bitchy again or worse yet, not get bitchy, let me go lean like a tyson chicken, and detonate from here to high hell? Is it even worth trying?

This is more frightening for me to test than the first time I hit the N2O switch.

Input?

 

Many ECUs seem to have defaults for when you go off of a load table.

But they are usually like no timing and 9:1AFR... My thoughts on this are if people can get away with 5psi on a small rotrex unit at stock redline using stock fuel system it should be possible to rev to 8k NA. And you are absolutely right, piston speed and acceleration starts to approach F1 speeds at our crank throw/stroke, however they are already made to run to 7k, which mine does happily when asked. I don't think periodically going to 8k will be a problem. We have a decent rod ratio, even with the 73mm bore x 89mm stroke..

I think ~1k rpm more, so like 7800rpm at 100kPa in a 1.5L @ ~90% VE is gonna be like 380cfm vs the ~350cfm we move at the OE redline, the ECU should be able to keep you at 12.5:1AFR or richer if it can pull it off under boost with almost 50% more air mass to tend to.

According to RCA you could wind out to 8k and not float any valves.. so just get a UEGO and work your way up from stock!

Now if there aren't VE reasons that will hurt flow up top be it cams/intake/exhaust that prohibit us, adding 1000rpm to the power band would be a huge modification and if its something that can be DIY that is even better.

Keep up the awesome work, the VTEC control thread was also very cool. Maybe between the two of these you can help some of us tailor our torque curves to our preference

And did I read you correctly where you say something about howl the ECU will fuel/spark cut @ WOT when the car is stationary or moving at less than 12mph?

This sounds like it could probably be made into a 2-step system with a little work. So some of us will be able to leave the line under full boost.. That sort of innovation may pave the way for 12-13sec L15 Fits!

 

after rereading this, things dont look so promising. Its clear that the injectors completely shut off for closed throttle events. Im just hoping it doesn't use the same mechanism for the rev limiter.

 

I seem to recall that the optimum shift points for the L15 were short of redline in the MT. Even with bolt-on type air-flow mods, I'm not sure that increasing the redline would improve acceleration at all if power is already trending down at the stock redline.

 

Another horrible idea from Lyon... Take a peak at a dyno chart for an L15, the motors aren't making power up that high. Revving that high will not create the power you're looking for, and it will put unnecessary wear on the valvetrain. At the end of the day its your car, but you seem to want to treat this motor like a b series, which it absolutely is not. This motor was built from the factory as an economy motor, if you want to rev higher and make power up there, rip the thing apart and build it for that, but in stock form you're only doing damage.

 

The trick is determining what components are restricting VE, if it is as easy as a manifold, header and exhaust this could easily be one of the better mods you could perform.

Not too mention cost effective. And on a boosted application, VE is increased by the compressor and you would see yet greater gains under pressure, because power would not taper off nearly as much or at all.

How do you know if you don't try?

 

Again, how do you know if you don't try. These are not facts spouting off, these are your opinions.

What contributions do you make to these forums besides antagonistic asinine comments? That seems to be all I read from you.

Lyon has more than once provided some insight through these experiments, and that is far more valuable than whatever it is you think you are sharing here.

Some of the attitudes on this forum and the willingness of certain posters to just make things up baffling. The engine already has an OE redline at 7k, it certainly seems that Lyon understands the implications in higher rpm as he does discuss piston mass acceleration and jerk, as well as friction and wear.

What is your point besides being contrarian and obnoxious?

 

My point is, you want to raise the redline of a motor that stops producing power at 5500 RPM's, therefore the only thing that will come of this is worn valvetrain that will either cause damage to a motor or break.

He may understand the theorys involved with the rotating assembly and movement of the pistons, but he fails to examine that the stock valve springs are only meant to compress/depress 6500 times per minute. Once you start moving them 8000 times a minute, they will heat up, not to mention that things start to get sloppy at that speed unless they're built for it.

What is your point in encouraging terrible ideas? You may think I'm an asshole, and I really don't give half a shit about your opinion of me.

The idea here is that if raising the redline in an L15 were a benefit why haven't any reputable companies shown up to track days revving their stock L15's to 8K.

 

You mean like Kraftwerks raising the rev limit with their card and Race Craft Academy re-flashing redline to 8k? And what exactly is your basis for deciding it is a terrible idea, and the stock valvetrain is apparently fine at 8k, as RCA has demonstrated. Much the same I hold no value to your opinion. You appear obstinate and close minded.

Again, what information or experiments do you have to contribute to the community? None?

Maybe it would be best for you to remain silent, and thought of as a fool, then to open your mouth and remove all doubt.

It sounds like you just want to rag on Lyon.

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Lyon, Keep trying new things and posting your excellent DIYs, ignore sheep like this guy and you will find success.

Trial and error is the only real way to determine what works and what doesn't.

There are people like gd3vbp on every forum who make these arbitrary rules for innovation and modification and it's only too funny to see how often these types are wrong and just making it up as they go because they feel what they think to be true.

Setting ambiguous limits on components they have often never even laid eyes on. Like all the morons who try and tell people like Kevin Kiggly that you can't rev a 100mm crank past 8k, and yet season after season constantly breaking records and shifting past 9k on the same engine. He recently went 8.2sec in the quarter on a 2.3L FWD by not listening to haters and fools like gd3vbp

B..b..but the rod ratios and piston slap! B..b..but valvetrain deflection! Except none of these were actually a problem in practice. The only issue was draining oil back to the pan after long WOT pulls. So he found a solution to that too by revising the stock HLA Regulator..

There is only one way to find what really works, and that is by experimenting.

And yes, in your own words gd3vbp, you are an "asshole." You have not even determined why or how the power production levels off, but you assume there is no way to remedy this? A few intake/exhaust mods would likely be all that is required.

The valvetrain is fine at 8k, and their already exist quenching surfaces on the piston tops and the valve hats where they seat. You will not melt the natrium filled exhaust valves by revving higher.

OE engineers expect people to miss shift and over-rev,the valvetrain is going to be plenty sturdy to see only 8k. Also, as far as the engine being built for economy... that argument doesn't mean anything. The engine block isn't going to just explode because you decided you had other plans. It is an engine, and a solid, proven one at that. Look at the SCCA retiring the Formula Ford Kent engine for the L15, look at the japanese endurance circuits using the L engine. There is a ton of potential here.

 

Please tell me....DSM now = Hondas? I don't see where that argument comes in.

also.....a drag car is far from a daily driven econobox.

 

Are you suggesting the engine knows what badge is on the hood? The same physics applies to both.

Do you guys like wake up, huff some ether and decide to post afterwards?

 

DSM's must know. They instinctively crank walk.

 

Aside from the personal attacks in your post, which have now been reported... what other mods does Lyon have at this point to support this motor up to 8K? None that I've seen, this motor runs out of breath at 5500 in stock form, revving it higher is useless and creates wear on items that are better off not being pushed to the limit.

What do you contribute to this "community" as you call it? All I've seen is namecalling.

 

Desperation is stinky cologne.

You realize that is a problem associated with the 7-bolt cranks, and even then a revised thrust washer and retorquing the mains under tension is all that is required to resolve it.

But lets ignore all the 550whp+ stock unopened block 6 and 7 bolts to focus on a problem that is not only rare, but really only occurs to people as ignorant of their internals as.. you.

How does it feel to know you can't address the subtance of my posts but instead have to make a tangential attack on something that is not really that tough to avoid in the first place.

So back on topic.. besides that fact that you cannot appreciate other makes or models, or even pretend to understand associated issues with them like crankwalk, what makes you think any of what I have had to say in this thread is untrue?

So you're saying I should hate on hondas 4cylinders for routinely running lean on cyl 3, or having toothpicks for conrods? Or make jokes about how they are anemic torqueless wonders?

Try growing up and out of your sad, myopic world view.

 

So because he may or may not have other VE mods, he shouldn't pioneer a new concept? Thats well stupid.

What do I contribute? How about hours composing tech posts and trading PMs with folks who have questions on everything from wheels and tires, to cams, manifolds, turbos, injectors, diagnostics an reading compressor maps, or brake upgrades etc.

Or exchanging phone calls and emails with groups like RCA, Bisimoto, Mahle, and Neukin to try and get new products to market?

Wear is a by-product of just driving the car, if you are performance oriented, this is just an expected part of the process. So you are free to not do this, but at the same time trying to tell him he has horrible ideas because unlike you he actually gets out and does the things he thinks of helps no one and provides no data or ideas and is just generally detrimental to the community.

And so what if in STOCK form it runs out of breath before 6k, great, but not everyone is stock, especially those considering raising the rev limit.

 

I appreciate other makes/models..I just got out of a Mitsu OMG...I'm just not a fan of unreliable, overweight pigs

 

This guy has a very valid point. The valve-train on the L15A wasn't engineered to rotate at the revolutions per minute that the OP will be subjecting the engine to. One bad scenario: valve float.

Look at Honda's B18C5, it has special valve springs that allow the engine to rotate at 8400 RPMs, (and it was engineered from the ground up to rotate, and operate in that range). However the peak power output for the engine is right around 7000 RPMs, and the power begins to drop off after that.

There are many other reasons one would not want to raise the rev-limiter. Another one being the fact that the car is not tuned for it, and it will not make any more power without a lot of other work (and upgraded performance parts). The other poster who said it will not make more power, just from raising the limiter, is absolutely correct. The power-band begins to drop off, even before you hit the factory rev-limiter, which is why real race car drivers shift gears at the peak-power RPM for their engine, not the red-line, or rev-limiter. There's no point in taking the engine up any more, if its not making any more power than it did a few hundred RPMs before. Taking the engine up 300, or 1000 RPMs more won't make the car faster if it makes peak horsepower 300, or 1000 RPMs before you decide to shift. It is completely dependent on the power-band of the engine.

And: Raising the power-band, or peak power of the engine, isn't nearly as important to most performance engineers, as improving the mid-range power, which is much more important on a racetrack/roadcourse, than peak power output.

 

Uh overweight? My 1G AWD weighed 2700lbs. My 1G FWD weighs 2480lbs. The 2G talon I sold weighed 3050lbs.

None of which were unreliable, because as shocking as it sounds, when you do routine inspection maintenance and supporting mods, cars last longer, crazy I know.

When you have a 20 year old platform driven by teenagers things get beat up and neglected. Shocking.

 

As far as valvefloat on the L15s:


I could write you a dissertation on what is involved with valvetrain and rotating assembly revving out past stock redlines.

I have a long rod, destroked 2.0 with dual valvesprings and Ti retainers that revs to 10.5k before power falls off.

This is running a SMIM, 3" exhaust and FP5r/11r cams.

The Fit will be fine at 8k in stock trim. To take full advantage of a raised rev-limit it is implicit that further tuning and mods would be necessary. This is a mystery to no one, and it does not detract from what Lyon is doing.

That is what I am trying to get across here.

And I am more than aware, as you can see from past posts or my tech thread, that area under the curve is far more important than peak output. That is not what we are discussing, this is about the merits of being able to wind out our little 1.5s further. This when complemented with the right mods can provide large gains.

 

Considering what they don't have.....2500 lbs is quite heavy