Alfa Pages

[prauguste]

Is there a rev limiter on P4. If I accelerate hard (which is quite often) it cuts out, I think when pushing it in second gear. Can't remember RPM. Any ideas?

[wille]

It's probably little over 7000rpm, can't remember exact number but 1.7 ie (8v) is limited to 6500.
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-Ville-

[Guest]

Thanks for that I must admit when I visited Squadra chip sight for reviews the indication was that P4s are rev limited.

[Pimp_Dudu]

[wille]

I'm not really sure what you mean, because if the car has a rev limiter (as practically every car in this world has) it's impossible to over-rev it just by accelerating. I've reached the limiter couple of times, and it's always been in 6500rpm. But if you change down with too much speed, then it's another story.
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-Ville-

[Maze123]

I think, what pimp_dudu means is, that if you double de-clutch when shifting down, the rev-limiter is not worth much if the revs in the new gear are higher than 6500! In that case, it doesn't work. I don't know why it doesn't work in that case, but as pimp_dudu, I've tried it too. Quite chocking to see the needle move that much into the red area!! The same happens if you push the accelerator to the floor while in neutral..In that case the rev-limiter doesn't work either!
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Alfa 33 1.7 16v '88 QV
http://www.bilgalleri.dk/html/gal_visbil.asp?ID=2498

[James Granger]

That's crazy! What's the point?

[BILL]

I have reached the rev limiter 2 or 3 times in the 3 years i have the car (second or third gear).I am not sure how high is it but its inside the reds.From what i understant it works as a cut off to the ignition of the car than to the fuel.I dont think you win something by revving to the limit ,all that you do is stresing the engine and the engine holders(dont know the exact word ,its those metal-ruber things that hold the engine to her possision).

[Pimp_Dudu]

exactly...u dont win anything at all...u really jsut hurt the engine...maybe just maybe u win tops 2-4hps but the result of that could a really screwed engine....Now when you're on let's say 4th and you're at about 6500rpms naturally under theory if u were to push it it one gear down to 3rd you'll go over the red line into something like 8000...right? But just by pushing it the gear down wont work since the syncro system and rev limiter won't allow you to go over the, and you'll end up hearing a "cruuuuunch". now you could push it IN the gear while it is CRUUUUNCHING but u'll end up killing your gear box or just braking the syncro ring. So what you do is double declutch. Meaning that you put the gear in neutral. (since in netural you can rev as high as u want since the rev limiter is turned off) while you're on 4th and 6500rpms and press the gas into 8000-8500rpms and then go quickly into gear 3rd while the rev are at 8000-8500...thus u'll get 3rd in without the crunch, wíthout brakign teh syncro and with 8500 revs controlling your engine The theory behind this is the same as double-declutching theory...all you do is "synchronize" the gears yourself.

[Guest]

[BILL]

For PIMP_DUDU You just make the engine rev high but the engine is not working,not producing power.Its like if you make the mistake and go from 4th gear to 3rd than to 5th.You make the engine to rev high from the Km you are already have.I hope i make some sense on what i am writing

[Maze123]

Guest - You wrote: "Sureley, if you floor the throttle in neutral, the engine will not rev beyond it's set limit"...Yes it will!! Don't try it, just believe me.. But you're right, there's no point in reving it higher than 6500, or maybe only 6000 (8v), becuase you dont gain any power up there. As for the 16v it's different.

Bill - I think I know what you mean.. You mean, that if you push it in 3rd instead of 5th by a mistake, the engine is not pulled around by it's own power, but by the power comming from the gearbox/the wheels..Right?!

Actually there's no point in this! Just dont go further than the rev-limiter allows you, which in some cases is to far becuase you dont gain any power at high revs, unless you have a chip installed, which, as far as I know, moves the rev-limiter and gives more power at high revs...
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Alfa 33 1.7 16v '88 QV
http://www.bilgalleri.dk/html/gal_visbil.asp?ID=2498

[gritsop]

Hi,

I would like to add my opinion also.

When the engine is eg in 4000 and you shift down from 5th to 3th then engine revs will rise but not actually from the throtle but from the wheels/gearbox giving a false rpm indication.
If you accelerate , then it is a different situation.

Virtually one can damage the engine if going in 5th gear/high revs and shifts down. The smaller gear ratios will drive the engine with more rpms , which will be far more than the upper rpm limit.

Bill is right - the rev limiter is located inside the distributor and actually it cuts the ignition towards the spark plugs.

In addition I have a book that says about braking with the use of the engine (by shifting down)
It says that since less fuel is inhaled from the engine AND the engine is forced to work in high revs than it should, then this stresses the pistons and rings for the simple fact that during these engine revs the amount of fuel for the idle is consumed.(since you don't press the accelerator pedal)
This book is published in the 70's for the carburator engines - I think that this theory should apply to todays cars even though technology has evolved. For sure the basic principles remain with no change.

So dont stress our engines for no reason. After all it is a strong point for our catalyst cars not to overhaul the motor from any aspect and bad use would be the most embarassing. Catalyst engines are designed to work in excel and it should be the last item to go wrong.

Regards,
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Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop

[paddy granger]

Well - depends how you look at it:

If you double-de-clutch, a bit of fuel is injected during the throttle blip

On the IAW injected engines (1351 cc), no fuel is injected into the engine when the throttle is released anyway, so it can't be too bad for the engine.

I am just a bit surprised that the fuel injected cars will not rev over the limiter in neutral - find it hard to believe but won't try it out obvioussly. If the engine will rev over the limiter in neutral, when will the limiter work?

[Maze123]

The limiter only works whenever the car is in gear, and you're accelerating...Well, I thought the limiter would work in neutral too, but after I once missed a shift from 2nd to 3rd, and pushed the accelerator down while in neutral, I realized it doesn't work in neutral! Haven't tried it since, and I' not planning to try it...
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Alfa 33 1.7 16v '88 QV
http://www.bilgalleri.dk/html/gal_visbil.asp?ID=2498

[Matt Stolton]

On the Carbed engines, the cut out is in the rotor arm, where a weight attached to a spring spins out wards, with increasing RPM. As it gets to a certain RPM, the weight has travelled sufficiently close to the dizzy cap, and shorts the HT to earth.

In an injected car, the ECU has a predetermined cut point, where it stops the sparks firing, but from the low voltage side, before the coil packs.

Because of this, the rotor for injected models, can be used on the carfbed models, thus letting you blow your engine at silly revs if you wish.

However, most standard carbed engines develop maximum power at around 6200 RPM (certainly my 1.7 ti showed a power run readout with max at 6225). This effect can be felt in 5th gear at top speed, as the engines maxes out at around this RPM, and gets no further. In lower gears, you can feel your self accelerating slower after 6200 ish RPM, than before.

However in suitably modified cars, with modified power curves, peak power can occur higher. This is why many after market chips raise the ECU cut out to somewhere between 7000-7500 rpm, as they assume you have made mods that allow extra air in, exhaust out, which will lead to a higher power at higher revs.

Still, none of those mods are worth doing, unless your cam belts are tip top condition, and you have balanced/lightened, and made strong your botom end. Quite simply, unless you are 110% about your engines condition, going past 7500rpm is asking for problems. This is why factory cut outs are as low as they are. However, if your 110% about your engine, going past its safe rev range probably wouldn't appeal any way.

To add weight to some of the other posts, you can obviously downshift, and use the wheels to spin the gearbox and engine to speeds beyond the limiter. However, not only are you spinning the engine at horrible speeds, the issue of lean chamber is also correct. Fueling may well be cut (your foots on the brake not the accelerator) as well as ignition on some injected models, so any spark that does make it into the chamber, will be igniting a very lean mixture. This can lead to holes in pistons etc, which is bad. Lloyd at clovertech showed me a customers piston, where he had been revving hard, beyond what the carb could deliver, and had burnt a hole down the side of the piston. This was due to the mixture being too lean at high RPM, and the piston overheating. Very nasty, and has written off the engine. Luckily the customers up for a 16V into his s2 conversion
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Regards

Matt

Ex Alfa 33 'GTA' (P4 with Knobs On)
Now cruising in a 166 3.2 Ti!!

[Lon]

The 33 16v engines have the rev limiter at 6850 rpm fitted in the ECU.

The 33 8v engine with ECU has a rev limit at around 6500 rpm..

The 33 8v engine's with carbs I don;t know the rev limiter setting but that one can be easily removed.

The limits are set just over the max power point, so a higher rpm will only give LESS power and torque.
You can modify the ECU with a Squadra Tuning chip, the rev limiter is then set to the NEW power/torque curve you get and means for the 16v engine a rev limit of 7300 rpm.
So this means a speed of aprrox. 200km/h in 4th gear at 7300 rpm

I have had my 33 16v many times in the rev. limiter on the track, but on normal roads I don't want to improve track records.... so the rev. limiter is not used very often on normal roads.. ( expept when sprinting at a traffic light offcourse )
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Registro Trentatre: http://www.alfaromeo33.nl

Alfa 33 1.7 S 16v QV '92

[Maze123]

Lon - Do you have a Squadra chip?
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Alfa 33 1.7 16v '88 QV
http://www.bilgalleri.dk/html/gal_visbil.asp?ID=2498

[Lon]

[GaryUK]

The reason that u can go over the rev limiter in neutral is the momentum of the engine carries it over the cut out point. But if you keep it full throttle then the engine will settle bouncing on the rev limiter.

[Eddie W]

Great answer Matt. Iwas just about to leap into print when I read your exposition. The carbed limiter is indeed centrifugal and it doesn't matter what antics you get up to in nuetral it is not sparking and therefor doesn't have combustion loads on the crank, which is not necessarily a good thing. All you rev. maniacs should bear in mind that the reciprocating loads increase as the square of the revs. As a generalisation the higher the revs, the higher the oil pressure to ensure that the oil film is maintained between big end shell and crankpin. However, having rebuilt one of our engines myself, I have to say that the bottom end with its crossbolt mains etc looked pretty bullet proof to me.
I would also like to relate an incident of hearsay about the Alfa bottom end; A local wrecker of Alfas decided, after a large number of cans at their Xmas party, to blow up a 1300 Sud in their workshop. the car was fired up and a large concrete block positionedso that the engine was sitting at max revs. Back to the beer while they waited for it to self destruct. After one and a half hours of this screaming machinary, the noise became too much and a new plan was devised to speed up the exercise. Solder up the rotor arm and it will go boom in minutes. After nearly 30 minutes at close to 9000 rpm it started to knock in the big ends and eventually seized. Not bad huh.
Alfa uber alles
Regards Eddie
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A LITTLE FURTHER A LITTLE FASTER

[GaryUK]

I put a solid rotor arm in when I scrapped my last 1.7 8v 33 and couldn't kill it through extreem rev abuse, had about 1/2 an hour racing it round the compound (all the lads at the scrappy joined in and were suitably impressed). Finally the clutch disc exploded!! Even the gearbox held out!!