Mi16 rev limiter

For what purpose?
I would guess that the rev limited was there to prevent any damage, unless of course you have made some alterations to the head and cams.
My S16 redlines at 7000 and cuts off firmly at that point, however max HP is reached at 7000 too.

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1995 306 S16
 
i can't see any reason to change it unless you have had some mods done but if you are going to rev a motor that far maybe a rotary is better for you (no malice intended)
my GTi6 redlines at 7000 and cut of is at 7300
it has only been at that point no more than prob 4-5 times in it's life and i have only ever hit the cut off twice
i think that the amount of piston speed at that amount of revs has got to be way into the extreme wear bracket
 
The engine is undergoing some modifications of course. I'd like to be able to set the rev limiter higher without having to have some sort of custom PROM made or something. The powerband of the motor will be pushed up about 500 RPM, and for some reason my limiter kicks in at exactly 7000. I always thought XU9J4s were supposed to be 7300 anyway...

-Joe
 
I'm surprised that the rev limiter comes in so low. Despite people's superstitions, most 4 cylinder engines made since 1960 (i.e. 5 main bearing engines) have to be reved way past 7000rpm to sustain any damage (so long as the oil is good). You would think an engine designed in the 1980's with twin cams and 16 valves would be unlikely to sustain damage until atleast 8500rpm. The manufacturers seem to put a very large factor of safety in their red line's and rev limiters. I've heard that the manufacturer suggested maximum for the Peugeot XN series pushrod engines is about 5800rpm, however taking them to 6500rpm or more seems to do them no harm, unless they're already damaged by something else (low oil, etc). Not that there is much point going that high in standard trim, unless your going up a really steep trail where the car will bog down at anything less than 6000rpm gear changes (I've taken my 504 and 404 on dirt trails that are that steep!).

Dave
 
I've heard many Mi16 tuners claim the stock motor will tolerate being spiked as high as 8800 RPM without any obvious problems.

My '84 STI XN6 has seen 6500 a few times and it still runs just fine. I find about 6000 RPM to be a good upshift point on mine. In other words, it balances out the power reaching the road--upshifting at around 6000 drops the engine to the point just before the beginning of the power band.

I have a few mods here and there which may have opened up a tiny bit of power up there.

What is the maximum speed for an XNx motor anyway? Has anyone ever found it?

-Joe
 
Joe,

I've taken standard XN1 engines (double barrel Solex carb) to 7000rpm on a number of occasions, with no adverse side effects. This is 100km/h (62mph)in 2nd gear in a 504.

I saw my father once take his XN1 504 to 7500 rpm. That engine was standard except for a double barrel 36mm Weber carb.

I often take my modified XN1 to 6500 rpm, just to "blow the cobwebs out". This motor has a modified cam, a slightly modified head, a lightened flywheel, a 32/36 Weber, a free flowing 12" diameter aircleaner, tubular headers and a 2.25" O.D. mandrel bent exhaust system with a Dynomax super-turbo front muffler and an expansion box resonator at the rear. Before I had the headers and 2.25" system fitted, this engine had a "rev limiter" effect at 6800rpm for some reason, but after I fitted the big exhaust it revved to 7000rpm with no trouble (I haven't tried to take it past 7000rpm). Like you, I usually find that 6000rpm is quite a good change up point.

I think Pugrambo might have taken a twin Webered XN2 much higher than 7500rpm, but I'll let him confirm or deny that. He might have a better idea than me of just how high they'll go before failure.

Personally I think that sustained revs above 6500rpm would cause premature valve gear wear (pushrods, springs, etc), although short burts to 7000rpm seem to be OK. Also, the XN engines have a less than ideal conrod length to stroke ratio (about 1.63, instead of the ideal 1.8 ratio of the XC series), which causes a bit of power loss to wall friction, because of conrod angularity.

The XN series of engines have a steel crankshaft, double valve springs, a double row timing chain, a very rigid engine block, and are oversquare, which help them survive some very extreme treatment.

Regards,
Dave
 
Joe,

Peugeot 16v engines are one of the best in the world.
You will have no problems reving it to 7500 rpm or even a spike to 8000rpm.
My 1.9 has been reved to 7000rpm on many occasions.
I have even hit 7500rpm while running a Vtir honda prelude.
I did encounter valve bounce over 7000rpm though.
Even though you may fall off the powercurve sometimes you need some revs to keep some momentum in a race.
As long as you are not using sustained revs you will not have any problems with a well looked after engine.
After all that's what multivalves engines
are designed for

Murat
 
thanks dave
has my father been telling you stories again ?
yes i did have a twin webered one and it went pretty well
has early Ti cam in it and made all the right induction noises when tromped on the loud pedal
i found out the hard way that things don't go the way they are meant to a lot of the time
i used to run up and down a very nice piece of road called the macquarie pass
it's 8km of winding mountain road going from the southern highlands to the coast towards wollongong
if you know the road you will know what i am talking about
anyway the pass trip used to take 5 mins most of the time
sometimes a little less but hardly ever any more
ran mobil one in the engine and things were always kept a check on
the engine quite often saw 7000rpm going up or down sometimes a little more (prob around 7500) but after a while the car started to lose power
push rods ended up bowed and it picked up a piston and scored the bore
the journeys were once or quite often twice a week for tafe
btw way that car was also lowered 3" all round and had 604 lower control arms on the front to increase neg camber
front had 3deg neg camber and rear had same
exhaust was 2" free flowing system and pretty loud but nice note
these days my cars go no where near those revs
that's bieng the story i think dave was talking about
also had another Ti but dave my father tells 2 stories better than i
1 the trip from goulburn to marulan
2 the trip from bathurst to goulburn
next time you are talking to him ask him about those ones <g>
 
Sean,

Did that twin webered engine have the 8.35:1 pistons or the 8.8:1 pistons? I know that the 8.35:1 pistons sometimes fail around the oil control ring and the top breaks off from the skirt, scoring the bore, etc. The 8.8:1 pistons seem to have a much more solid construction.

Yeah, I know Maquarie Pass. It's awesome, so long as you don't get stuck behind a truck or a line of traffic. I had a fast ride down there one night in 1993 in a friend's modified Datsun 1600, and his CB radio to speak to the truckies helped alot during overtaking on the pass. Incidently we returned to his place at Robertson via Kangaroo Valley that night. That was interesting too, especially when we spun out on one of the curves going up towards Fitzroy Falls. Fortunately we didn't hit anything.

I think it was you who told me about you're twin Webered 504, when I was talking to you while we were looking under the bonnet of Michaels Loney's twin webered 404 at the 1996 Easter pagent. I saw your white 504 TI when I ran into you and your father at the 1993 12 hour race at Bathurst in 1992. I think you and your father told me about the Goulburn to Marulan trip then (was that the 120mph trip following an LTI?). I think you mentioned at the 96 easter pagent that the TI motor blew after you left Bathurst.

Dave
 
dave
pretty sure it had the 8.35:1 pistons in that motor
and yes same car that did the 120,ph trip from goulburn to marulan following roger kreft i think his name was from canberra, mind you i had both parents in the car and the one that was egging me on more was of course my mother
if anyone knows my mother they would understand what i am talking about <g>
that same car also did the trip from bathurst to goulburn in 1993 out through all the nice dirt back roads
we were warned that the road then was not really fit for cars but we went anyway and 2hrs later we were sitting in a chinese restuarant eating dinner in goulbourn 2 hours later
funny thing though father didn't say a lot on the trip but he did have a big grin on his face lol
 
dave
pretty sure it had the 8.35:1 pistons in that motor
and yes same car that did the 120,ph trip from goulburn to marulan following roger kreft i think his name was from canberra, mind you i had both parents in the car and the one that was egging me on more was of course my mother
if anyone knows my mother they would understand what i am talking about <g>
that same car also did the trip from bathurst to goulburn in 1993 out through all the nice dirt back roads
we were warned that the road then was not really fit for cars but we went anyway and 2hrs later we were sitting in a chinese restuarant eating dinner in goulbourn 2 hours later
funny thing though father didn't say a lot on the trip but he did have a big grin on his face lol
and yes the motor picked up a piston and scored the bore and at around the same time the liner seals went and i had white oil in the sump
 
405 Mi16x4 have a different chip which allows 7300 redline. If you have an imported Mi16, it's an easy job to drop in a x4 chip. If you have an Australian model it's a bit harder as there wasn't a pollution model x4.
 
all Australian spec 405 1.9 MI16 had a rev limiter at 7300 rpm and i know mine goes there very regularly and it loves it
but thee is no point in going to those revs unless some relevant engine mods have been done
 
My 306 S16 cuts out hard at 7000rpm, but the engine is basically identical to the Mi16.
Any reason for this?
 
So basically, the concensus is that there is no "easy" way to bump the rev limiter--reprogramming is the only way? That sucks...

-Joe
 
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