Cut spark instead of fuel at rev limiter?

[_R_J_K_]

When a VP 5 litre hits the rev limiter, is it possible to tune it in such a way as to have the ECU cut the spark as opposed to cut the fuel supply? Or is this not possible because of the dizzy setup?

[greenfoam]

You can do it if you go aftermarket ignition

[Cursed CX8]

out of interest? why would you want this to happen?
I honestly dont know, im not asking a smart arse quesetion

[immortality]

as foam mentioned after market ignition systems like MSD/Crane do this. it's known as a soft rev limiter. basically it allows you rev the engine right up to the limiter without it "bouncing" like it does with the factory rev limiter. with the factory limiter if you free revved the engine in neutral the engine would rev past the limiter before it could catch it. with a ignition based limiter this won't happen.

[Matt_vp]

out of interest? why would you want this to happen?
I honestly dont know, im not asking a smart arse quesetion

Would rather have the cyclinders not fire over going lean, when it fires and the isnt enough fuel in the chamber. Probly not worth it with a standard motor and setup.
I dont like hitting the limiter for this reason. I might just be pananiod because ive been through a few engines.
Matt

[_R_J_K_]

out of interest? why would you want this to happen?
I honestly dont know, im not asking a smart arse quesetion

Some of my mates are into Japanese cars, and were talking about the "Bee*R" rev limiter system (I have no idea what it's all about) that are typically used on Japanese cars sometimes, some after market ECUs also support their own version of this system. If you go and watch some of the videos around the net of these cars doing burnouts, they typically shoot flames out the back because of the unburnt fuel and make tons of noise,

So... My mate with the 5 litre hooked on to this idea (because he wants his burnouts to be spectacular, typical wank factor thing), and wondered if it could be implemented with a memcal retune.

There are good reasons for this as mentioned by immortality and Matt_VP, there are also a few downsides to it too. Me personally, I'd just rather keep away from the rev limiter to be honest.

[Matt_vp]

Some of my mates are into Japanese cars, and were talking about the "Bee*R" rev limiter system (I have no idea what it's all about) that are typically used on Japanese cars sometimes, some after market ECUs also support their own version of this system. If you go and watch some of the videos around the net of these cars doing burnouts, they typically shoot flames out the back because of the unburnt fuel and make tons of noise,

So... My mate with the 5 litre hooked on to this idea (because he wants his burnouts to be spectacular, typical wank factor thing), and wondered if it could be implemented with a memcal retune.

There are good reasons for this as mentioned by immortality and Matt_VP, there are also a few downsides to it too. Me personally, I'd just rather keep away from the rev limiter to be honest.

Does your mate have a turbo on his v8?
Bee r is mainy used to build boost for a launch and also good for burnouts. Something to do with the extra fuel making the zorst hotter and making the engine make boost with no load, aswell
as beeing a good quality rev limiter.

Taken from: http://www.neweraparts.com/Default.a...0&ProductID=17

This is Bee*R’s popular two-stage ignition cutting rev-limiter. It is used to prevent damage arising from over-revving your engine. Part of the reason for its popularity is the large flames and loud bangs it produces from the exhaust when active!

The way in which it works differs from the factory rev limiter in that it is an ignition cut, as opposed to a fuel cut. The reason for this is because if an engine (particularly turbocharged) regularly hits a fuel-cut rev limit (such as in high performance driving, or particularly drifting) engine damage can arise due to the lean condition produced when the original ECU shuts off the fuel pump. The BEE*R rev-limiter allows fuel to pass into the engine still, limiting engine speed by disabling the ignition signal. The Bee*R rev limiter is fully adjustable in 500rpm increments, for safety reasons allowing only a lower rev-limit to be configured than standard. If you have spent a lot of money tuning your engine, or are running at high RPM’s for extended periods of time, it could be recommended to run a lower rev-limit to prolong engine life. Both Formula 1 and JGTC cars use ignition cutting rev limiters, so it is a fully race proven concept.

The Bee*R can also be used as a “two stage rev limiter”, as an aid for launching your car. The Bee*R is configurable for two different rev-limits. A lower rev limit can be activated by a switch, the handbrake switch often being used. This configurable lower limit, can be set to the optimum RPM to launch your particular car from in 500rpm increments. When the handbrake is released, the usual rev limit comes into action, allowing quick launches, and full performance down the strip.

The Bee*R rev-limiter has another final neat feature. The gain control knob allows you to adjust the frequency of the ignition cut. This in turn changes the frequency and sound of the flames and bangs from your exhaust!

Available for use with all rotary, 4 and 6 cylinder engines. (No V8 application)

Matt

[greenfoam]

Mostly people in burnout comps like to hold the cars on the limiter once and a while during the burnout since it adds to the spectical. The ignition cut limiters soft different/better most different so and different is cool. This is why people like to run them. I'd also be dodgy on fuel cut limiters on a turbo car that was tuned on the limit

[Mungus]

In keeping with the theme, can i ask a question. I just got a 2010 SSV Sporty with 6.0ltr L76 with AFM and 6sp auto with active select. Just took it for a spin out to the 130km/h zone and checked out the manual shift mode and sport mode and to see how she goes now that i have run it in a bit (750km total) What i found sounds similar but not sure which one. In 1st just before redline, which looks like 6000rpm by the dial, but at about 5800 the engine dies. I think it then tried and died as i went for 1st again not second (haven't quite got used to which way yet) Tried again and seemed to time 1st to 2nd just as it cut out and got a small cough as i hit second. 2nd to third was good timed it just before. Does anyone know what they have doing this or should i post elsewhere? Also in Park it wont let you rev it past about 4000rpm, won't even pop up past it for a bit?

[Matt_vp]

In keeping with the theme, can i ask a question. I just got a 2010 SSV Sporty with 6.0ltr L76 with AFM and 6sp auto with active select. Just took it for a spin out to the 130km/h zone and checked out the manual shift mode and sport mode and to see how she goes now that i have run it in a bit (750km total) What i found sounds similar but not sure which one. In 1st just before redline, which looks like 6000rpm by the dial, but at about 5800 the engine dies. I think it then tried and died as i went for 1st again not second (haven't quite got used to which way yet) Tried again and seemed to time 1st to 2nd just as it cut out and got a small cough as i hit second. 2nd to third was good timed it just before. Does anyone know what they have doing this or should i post elsewhere? Also in Park it wont let you rev it past about 4000rpm, won't even pop up past it for a bit?

For starters why rev it so high in netural? You are probly hitting the limiter which i wouldn't be doing on a motor with 750kms on it.
Matt

[Mungus]

I gave it a poke in park to show a mate how quite they are and that's when i noticed it flatline @ around 4000. It's not going to damage anything. Don't you think the engine has been run and checked at the factory! I hope they checked it could rev free before i bought it!

[Mungus]

For starters why rev it so high in netural? You are probly hitting the limiter which i wouldn't be doing on a motor with 750kms on it.
Matt

Just had a second thought about your comment! Do you mean that even though i only saw 4000 on the tacho the engine itself had already been to redline then cut and the tacho wasn't fast enough?

[Matt_vp]

No i mean when you are flogging your car that has 750kms on the clock, you are hitting the limiter in first before you rip 2nd. But hay your car to distroy. It might have been run and tested before you got it, but the engine is still getting run in. They dont run you engine in for you on a engine dyno or anything. Its assembled, then tested, then sold.
Good luck in the future with you motor. The 4000rpm in park is probly a safty factor for stupidity.
Matt

[Mungus]

No i mean when you are flogging your car that has 750kms on the clock, you are hitting the limiter in first before you rip 2nd. But hay your car to distroy. It might have been run and tested before you got it, but the engine is still getting run in. They dont run you engine in for you on a engine dyno or anything. Its assembled, then tested, then sold.
Good luck in the future with you motor. The 4000rpm in park is probly a safty factor for stupidity.
Matt

Matt, I'm sorry you believe i am flogging my car. I am not. I have run it in as required by the dealership for 500k, using the rev range and driving it like i would normally. Of course being my only new car of this caliber for 30years, i then wanted to see what it could do. I have tried this three times; twice in active select mkanual and once in sport mode auto!!! If that is flogging it then thank christ it has a rev limiter and maybe they should set it a lot lower to protect this engine. Maybe, seeing as though you don't bother answering my question, you should tell me how long it will really take to run in, how, why, and apart from having a redline limit, what revs i can take it to on the odd occassion. But really don't worry as this is not even my thread. Just thought someone might be able to answer my question simply.

[Matt_vp]

I did answer your question. I said you are probly hitting the limiter.
I did hear something about the new 6 speed auto double clutching itself, in a sence, than cutting spark to help match the engine speed to the next gear before changing, but i dont know any facts on the subject so i didn't comment on it.
Maybe you should ring holden and ask them what is going on. lol
Matt

[one_and_only2004]

would a Bee*R limiter work on a commodore?

[Matt_vp]

Yeah it can be made to work.
Matt

[one_and_only2004]

When you say it "can" be made to work, is it any trickier than wiring one into a supra or silvia?

[danja]

No i mean when you are flogging your car that has 750kms on the clock, you are hitting the limiter in first before you rip 2nd. But hay your car to distroy. It might have been run and tested before you got it, but the engine is still getting run in. They dont run you engine in for you on a engine dyno or anything. Its assembled, then tested, then sold.
Good luck in the future with you motor. The 4000rpm in park is probly a safty factor for stupidity.
Matt

I seem to recall seeing a video of an engine assembly line, where one of the steps after it's been fully assembled was to rev it at high RPM for about a minute? I've also heard from numerous places that modern engines are pre-broken in by the time you get hold of the car, and that the break-in period is much less crucial than it used to be in the past.

It also seems to be a highly contentious topic about how running-in should actually be done. Manufacturers tend to say "take it easy", many mechanics claim that a good flogging helps the piston rings bed in against the liners better or some such.

That said I'd still follow whatever the manufacturer recommendations are simply because I assume they know best having designed the thing.

[acarmody]

If you cut the spark but not the fuel supply, won't you be dumping fuel down the exhaust and ruining your cats? Assuming your running cat.

[crazybiker]

It also seems to be a highly contentious topic about how running-in should actually be done. Manufacturers tend to say "take it easy", many mechanics claim that a good flogging helps the piston rings bed in against the liners better or some such.

That said I'd still follow whatever the manufacturer recommendations are simply because I assume they know best having designed the thing.

As have I. I've heard with boat motors aswell that your meant to do the same thing. But to me, it just doesn't seem normal, so I always take care running in a motor.

[Matt_vp]

When you say it "can" be made to work, is it any trickier than wiring one into a supra or silvia?

No not really, depend on what type of commodore.

I seem to recall seeing a video of an engine assembly line, where one of the steps after it's been fully assembled was to rev it at high RPM for about a minute? I've also heard from numerous places that modern engines are pre-broken in by the time you get hold of the car, and that the break-in period is much less crucial than it used to be in the past.

It also seems to be a highly contentious topic about how running-in should actually be done. Manufacturers tend to say "take it easy", many mechanics claim that a good flogging helps the piston rings bed in against the liners better or some such.

That said I'd still follow whatever the manufacturer recommendations are simply because I assume they know best having designed the thing.

Mechanic tell ya to flog it because it means more work for them.

Maybe that inital 1 min of high revs beds every thing in but if the engine breaks during that minute what happens. They throw it in the bin and start again, if your engine blows up in a new car, what happens. It goes to manufacturer and they plug there computer into it. Check the top rpm, how many times the limiter has been hit, top speed ect. Then decide if they want to give you a new engine or if u will be paying for it. Seen it happen to a mate in a new falcon at then end of 08.

Seen blokes with dirt bikes say the same thing about flogging it, and others run it in properly, the ones that got flogged had a very short life compared to the ones that are properly run in.

Im no mechanic, but do work in the metal industry and can see the need to run large chuncks of alloy with lots of moving parts made out of various steels in.

If you cut the spark but not the fuel supply, won't you be dumping fuel down the exhaust and ruining your cats? Assuming your running cat.

If you have modified your car enough to need a spark cut limiter, im sure you would have steel or empty cats in your car.

All in all i think spark cut is better than fuel cut on highly modified cars or cars running FI with high boost.
Matt

[greenfoam]

They do run new motors at high revs as soon as they come off the production line to make sure they wont break. But I allways wonder how many have cracks and *almost* broke after that effort . But I guess the factory have it worked out how long you need to run them and how fast for any flaws to break loose

[Lost_Pete]

Based on some work we did on Subarus.

Fuel cut is much easier on your engine than ignition cut. Assuming your engine has multiport fuel injection.

If you cut the fuel the cylinder just pumps air. The O2 sensor will report a lean exhaust but it is really only air, not a lean mixture.

If you cut the ignition you fill the exhaust with raw fuel so that when you come off the rev limiter you will get a backfire in the exhaust. The raw fuel can damage your cats and the backfire does not help either. In addition the backfire can stress your valves as it tries to push the exhaust valve open. We had some Subarus dislodge their valve shims when they tried using ignition cut.

Of course if you run carbs or single point injection then you are limited in your choice of rev limiters.

[danja]

A little off-topic, but still interesting - a video of an engine assembly line. They don't show it being run-in, but they do mention it at then end. Perhaps more interesting is that the engine looks like it might actually be the HFV6?!



Another episode from that show where they show the block itself being made: