Safe RPM in an AU6

[The Monty]

Hey guys, car is going in for a tune in a couple of weeks (again).
I have the limiter set at around 6200 at the moment, which is all good, but Id like it a little higher.
I have held the old monty to just over 6500rpm, but wouldnt have done it again in a hurry.
I want to know whats generally regarded as a "safe(ish)" limit to have it set to.
Car should be making peak power at around 5500plus, and I wanted to get the limiter upped to 6500to drop me right into a good bit of power when it changes gears.
What do you guys think?

[Mr Hardware]

are you happy with dropping in a new donk if need be? then go for it.
if not? then keep her at a happy level.

[The Monty]

Well, thats what the question was, what is this happy level you talk of?

[rob_liss_lms10]

Theres not much point going past the max power output, I would suggest whilst on the dyno find out where it starts dropping power and then set the limit 200revs past that. ie. if the power curve starts to fall at 6100rpm, there is no point reving to 6500 cause you are just flooging a dead horse.

[T3man]

What he said ...

[Mr_4.0]

i wouldnt rev any ea-au motor past 6000rpm to be honest.

they have a big stroke. make no power beyond that.

[RG]

Originally Posted by Mr_4.0

i wouldnt rev any ea-au motor past 6000rpm to be honest.

they have a big stroke. make no power beyond that.

At the max, especially on a stock bottom end.

I can just see a 6500rpm BOOM!!!!

[kcej]

Originally Posted by rob_liss_lms10

Theres not much point going past the max power output, I would suggest whilst on the dyno find out where it starts dropping power and then set the limit 200revs past that. ie. if the power curve starts to fall at 6100rpm, there is no point reving to 6500 cause you are just flooging a dead horse.

If we are talking automatics, I think you're wrong (just my opinion, but my reason follows....)

If peak power is at 6100, then isn't it possible you might still have more power at, say, 6500 in second than you are going to get when it drops into third and the revs decrease to suit the wheel speed in the higher gear. It would depend entirely on the shape of the power curve. If the drop after "peak" is MUCH more dramatic than the curve up to peak is, then yeah, you may be right, but I would still bet that 400 revs over "peak" in a lower gear would still be giving more acceleration than you are going to get at the entry point to your higher gear.

If its a manual, then of course you are 100% RIGHT.(driven properly)

[The Monty]

I make 152KW at 4900rpm atm. Cam and head once fuel can be pumped in will make max power at 5500rpm (has done before it was detuned). So say I make 160kw @ 5500rpm. With the tune as it is, and spinning at 4900 rpm and making 152kw, it still makes 140 @ 6200rpm. So say Im making the said 160@5500, I may still be making 150 odd @ 6200rpm. Id love to give it that extra couple of hundred RPM so when I change gears, its sitting in a nice big heap of power.
I know Stiddy used to spin to 7200, but we all know how that ended up.
Thanks for the input, Ill let you know what we figure out.

[The Monty]

Oh, and just for comparison sake, about flogging a dead horse over 6000rpm. In the Monty at the drags, if I let it change at 6000rpm, I would run 15.2's.
Made peak power @ 4900rpm, 133kw.
If I held it over the line in second (148km/h) and let it go to just over 6200 in first, I would run 14.9.
May seem like flogging a dead horse, but thats a big difference.

[Fordfan4u]

6500-6600rpm would be where its at... anything above that would be overkill unless the engine was built to do it.
Get rid of your chiptorque, get an adjustable fuel pressure reg, play with the vernier gear and get it re tuned with an edit. Make some better power. You've got a 3000rpm stall, no point power coming on strong under that.

[The Monty]

Im using the edit, not a Chiptorque chip. I just get it tuned at Chiptorque. I thought thats about where its at, had a fiddle with vernier gear, went to 6 degrees advanced, and apart from a little bit more down low, I didnt feel any difference between 0-4-6* advanced.
I havent heard of many 6's letting go from big RPM (apart from Stiddy), but everyone seems to know where the limit is.
Elite auto said take it to 6500, I think I will.

[blueoval]

Can I ask ya what work was done to the head, and what kind of flow specs you were getting The Monty?

[The Monty]

It was just cleaned up of dags and castings I think, cleaned up the ports, shaved 12 thou and flows 288 (I think) hp @ .600

[blueoval]

Thanks for that info. That kind of explains who your able to rev your car to 6000rpm and still make power.

Thats pretty good if you can do that. The max I rev mine to is 5500 but its rare I will get it to that point unless I feel the 'need' to get max power. Most of the time I rev it to 4500-5000rpm if I give it some.

I think I could be going where your going in future. Not necessarily to look for more revs, but definitely more flow with the head porting and a larger cam.

I have a spare already reconditioned head already, and am thinking of going a saloon car grind cam. But thats OT. sorry about that :P

I would say that with yours though, you should only see 6500rpm on rare occasions on a stock bottom end.

[Fordfan4u]

Originally Posted by The Monty

Im using the edit, not a Chiptorque chip. I just get it tuned at Chiptorque. I thought thats about where its at, had a fiddle with vernier gear, went to 6 degrees advanced, and apart from a little bit more down low, I didnt feel any difference between 0-4-6* advanced.
I havent heard of many 6's letting go from big RPM (apart from Stiddy), but everyone seems to know where the limit is.
Elite auto said take it to 6500, I think I will.

Not many people spin theirs as high as 7200rpm. Ive only heard of a handful that have, those people are pushing the envelope. Alot of 6's have problems with excessive revs, the AU bottom ends are incredibly strong but having said that there is a limit.
Ask Elite why not to spin yours to 7000rpm? powerband or the bottom end not taking it? Alot will say because no power up that high. get the head/cam to suit and you can, but then the bottom end comes into it. Again pushing the envelope to see how far you can go.
I find it odd that you felt no difference when changing settings on your vernier gear.
All good, well good luck with whatever it is your trying to achieve.

[The Monty]

I thought it was quite odd as well, but this coming from a guy who thought his car went slower with the flash tune, then ran .5 of a second quicker, so Im not that good of a judge.
When it was set at 4* and was tuned it made 139kw. When I put it on another dyno at 0* it made 138.8kw, so I dont think there was much of a difference at all. In saying that everyone Ive spoken to with a surecam have all advanced theres from between 2-6* and have always made there results there.

[FreddyDUZ747]

I see max power is a around 5000rpm,does it hold that power to 6500rpm?

At a guess the extra time to spinup an extra 1500rpm on your motor you would not give the quicker ET.Id say it would take 5tenths to get that extra rpm and i dont think youll get that back by raising the gear change rpm.

An more aggressive final drive would be better and allow you that consistent pull without having to rev the cane out of it.

[The Monty]

I have 3.9's, I dont think it will need more agressive gears, lol.

[OED666]

I accidentally selected 2nd at 110km/h with 4.11's.. Motor rev'd its nana off (I have an AU XR6 Motor) and its still alive. I'd love a $$$ for everytime mine has seen 6000+rpm, and made sweet love to the limiter on the skid pan in a 5 minutes.

I think mine makes peak power a bit over 5200rpm, but Chiptorque said at the drags change around 5800rpm to keep in the peak powerband for a longer time.

[Sox]

Originally Posted by The Monty

I thought it was quite odd as well, but this coming from a guy who thought his car went slower with the flash tune, then ran .5 of a second quicker, so Im not that good of a judge.
When it was set at 4* and was tuned it made 139kw. When I put it on another dyno at 0* it made 138.8kw, so I dont think there was much of a difference at all. In saying that everyone Ive spoken to with a surecam have all advanced theres from between 2-6* and have always made there results there.

Advancing a cam generally shifts the powerband lower in the rev range. Retarding it shifts the power peak upwards.

As far as rpm limit is concerned, normally it wouldn't make a lot of sense revving much beyond 5500 if the peak power is at 4900.

However with these I6's, you want the next gear to be above the BBM change over, which is 3800rpm.
with a manual I6 you need to rev to over 5500 to achieve that. An auto would need more because of the huge gap between cogs.
If revs fell below 3800, it makes quite a difference, hence your improved 400m time.

So to answer your question, yes rev it as high as is needed to make the next ratio only drop to 4000rpm (to be safely above the 3800). If that is 6200, then set the limiter at 6300.

The I6 is horribly undersquare and piston speed at 6500rpm is very high, so don't push it any further than absolutely necessary unless you have decent pistons etc.
My guess is that a standard AU I6 in good condition is good for the occasional blast to 6500, and even rare over-revs to probably 7000rpm.
But why bother if it is of no benefit.

More is not always better, and there is a point where you will go backwards if revving to high.

I'd probably be looking at a better cam if wanting to rev that high too, your figures seem pretty low considering the other mods you have.

[The Monty]

I completely agree.
Figures will climb. like I said, was making peak power at 5500 (dodgy tune, long story). Took it too another shop and it made 20 15kw more at 600rpm lower, and was backed off at that point due to fuel delivery. On the 31st it goes back in with everything fixed, and should be up around 155-160, with a big stall, thats a quite good number for the AU auto.
Ive seen manual cars on the same dyno (au's) pull 150kw and run 14.5's all day.
Your answer is exactly what I was after, I will test and see what gear is needed to ensure I am above 3800 between each gear change.
Just seems to want keep pushing past 6200 and feels to me as if its changing early.
Ask Blackers10 or FS5, both have been in the car and commented how it never even feels like running out of puff when getting over 6k.
Ill have a chat to the guys at Chiptorque and see what they have to say,
Thanks Sox.

[OED666]

Mine also feels like the 6000rpm limiter is destroying the fun. haha..

[Windsor220]

Give 8000rpm a go. See if you can get down the qaurter in just first gear.

[The Monty]

I would but the auto smells funny when I attempt that




Oh, and I dont have V-Tec