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Discussion Starter #1
Hi Folks,
I have had my 3.0 12v 164 engine in my GTV6 for a couple of years now and thought I would just put this out there as I don’t recall seeing anyone else ask/comment about it…

What should the redline be for a 3.0 12v 164 motor? In doing the swap I have kept all of the 2.5 running gear, I have the Greg Gordon intake and CSC headers but they were on the 2.5 as well. The 2.5 would happily rev to 7k rpm >:) (not a lot of point to it but it would happily get there) but the 3.0 will start to sputter at approx. 5800 rpm like it is hitting a limiter but there is no limiter in place – otherwise I wouldn’t know that the 2.5 could hit 7k rpm…

Do others have a similar experience? An experienced racer from the club had a similar thing and suspects it has to do with cams – thoughts??

I have come to live with the new rev limit but curious to know why I have to (and if there is something cheaper than spending $1k+ on new cams etc that can fix/change it)
Cheers
Marty
 

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Richard Jemison
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Rev limits

There are actually two, one controls the fuel ijection, the other spark...
Al Mitchell (Red Crown racing) and Ed (alfaparticle) has explored this throughly
 

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Yeah, but as I read it martym00se72 is using an Australian delivered 2.5 ECU, harness, distributor and ignition module. These do not have a rev limiter in the ECU or ignition module. They use a spring loaded rotor arm - if you scroll down this link http://www.alfagtv6.com/discus/messages/199/1211.html?0 there is a picture of one - it cuts out at 6300 rpm using centrifugal force. Replacing this rev limited rotor arm with a standard Bosch rotor arm removes the rev limiter from the Australian delivered 12V 2.5 - well it makes it high enough that I've never hit it.

Then again I may have read it wrong and martym00se72 isn't using an Australian delivered 2.5 ECU, harness, distributor and ignition module with the 164 3.0 12V in his car.
 

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Rob Steele and I have both experienced misfiring above about 5800 rpm with Megasquirt engine management. We found that the dwell time was critical. At 6000 rpm the spark cycle time is .003 seconds and that is insufficient to charge the coil fully between sparks. I installed a Crane Hi-6 CD ignition in my car and it will now rev beyond 7000 rpm. But it really does not need to rev so high as even with performance cams, peak power is around 6000 rpm.
 

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Discussion Starter #6
tpalfa is right - Aust delivered harness etc without the rev limited rotor arm - it freely revved to 7k with the 2.5 and has same dizzy, etc in place for the 3.0 - I know it gets to a point where there is little to be gained by revving it any further but 5500 to 5800 rpm seems a bit low I thought for just a 500cc capacity increase...
 

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It could be the ignition amplifier at 4800 rpm my car would stutter like it was rev limited when I swapped out an amp from an Alfa75 it now revs way past 6 easily I also removed the rev limiting rotor
 

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this really depends on your set-up. you have to take into account the cams you are using, injectors,exhaust, power curve etc. the only sure way is to get it dynoed by a reputable dyno operator who is familiar with the type of ECU and software you intend using.. When I had my 12V race engine NA on its initial run it ran to 9000rpm as the gearing was too short on the circuit during the test . It had larger injectors, electric fuel pump, a modified dizzy, 13:1 compression. shotpeened rods, larger plenum runners and lasted for over 10 years without a rebuild . we also did a lot of longer distance events 6Hr RACES. At that time we were using Haltech F6? ECU and always revved to 7500rpm which is about the limit for standard shotpeened RODS
 

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Discussion Starter #10
Stock internals, electrics ECU etc, taken/resued from the 2.5 when I did the swap. Only looking to use the redline per 2.5 tacho so an extra 3-400 rpm beyond 5800. I don't want to start thinking about valve float etc etc etc for stupidly high revs. Those few extra revs would help hold a gear a few seconds longer - good for the twisty stuff...
 

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Discussion Starter #12
So - what a difference 30 bucks can make! I put in some new plugs NGK BP6ES (has BP7ES before) and it was like I had put in a new engine! Happily revved past 6k. Have had issues with rich running/fouling plugs and a intermittently high idle - still have those so work still to be done, but the simple act of changing the plugs has made the issues seem less severe. So of course I went for a tune up run for a couple of hours Sunday morning and after several weeks of not having driven the car - I came home with a smile only an Alfa can give you :D
 
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