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firefox · Post by **firefox** » Thu Aug 16, 2007 12:57 am

there are 2 rev limiters in the stock 3l Jetronic with Cat.... checked it with bosch....
The one in the Fuel ECU is set at 6250rpm und the one in the Sparkcomputer ist set at 6700rpm.

I control my car with megasquirt and I allways hit the rev limiter at 6700 because I was driving with the original sparkbox and just control fuel at the moment. But it was harmful to the cat if you only use the spark revlimiter and dont shut off the fuel...

Made that mistake too..... , driving wihtout a cat is better anyway

x-rad · Post by **x-rad** » Sat Aug 18, 2007 4:43 am

good research there firefox!

Cboxoak · Post by **Cboxoak** » Sun Aug 19, 2007 5:14 pm

firefox wrote:there are 2 rev limiters in the stock 3l Jetronic with Cat.... checked it with bosch....
The one in the Fuel ECU is set at 6250rpm und the one in the Sparkcomputer ist set at 6700rpm.

I control my car with megasquirt and I allways hit the rev limiter at 6700 because I was driving with the original sparkbox and just control fuel at the moment. But it was harmful to the cat if you only use the spark revlimiter and dont shut off the fuel... Made that mistake too..... , driving wihtout a cat is better anyway

Hmm... interesting info.

I have the original 2,5 fuel ecu right beside me (Bosch 0 280 001 117) and some Alfa-mech told me that this 2,5 has no rev.limiter in it..? He says that a 3.0l runs fine on it - but I still need another Sparkcomputer cause mine cuts @5700 rpm

Can anybody confirm/decline this?

x-rad · Post by **x-rad** » Mon Aug 20, 2007 1:51 pm

which engine and which spark ign computer do you have...?

Cboxoak · Post by **Cboxoak** » Mon Aug 20, 2007 10:03 pm

OK... short summary:

Engine: 3.0 V6 12v from Alfa 75/Milano
Fuel ecu: Bosch Jetronic 0 280 001 134
Ignition box: Bosch 0 227 921 036
Rev limit: app. @ 5700

Gearbox from a 75/Milano 1.8 Turbo

Goal: More Horsepower

Problem #1:
Need more revs due to fastroad Columbo & Bariani Cams = engine lacks torque below 4000 revs
Now: 234 NM

Max torque with orignal cams: 250-260 NM

Solution #1:
Another stock Bosch Igniton and ECU with higher rev limiter, or no limit at all. Which one?

Solution #2:
Megasquirt - but that's kindda expensive so I'll give other stock solutions a shot first...

Problem #2:
Have AFM from BMW 535i for more air. Engine runs on it, but clearly needs more fuel to rev properly

Solution: "Squeeze" spring on orignal fuel pressure regulator

or

adjustable fuel pressure regulator.

I would like a regulator that fits where the original one is located to avoid to extend hoses in engine bay

Where do I find such a thing?

x-rad · Post by **x-rad** » Tue Aug 21, 2007 11:29 am

I don't think raising your fuel pressure by even a few lbs will increase injector flow significantly. You either need bigger injectors running at standard duty cycle or change fuel computer.

Mats · Post by **Mats** » Tue Aug 21, 2007 11:39 am

The flow will increase by the square root of the pressure increase.

Cboxoak · Post by **Cboxoak** » Tue Aug 21, 2007 2:23 pm

x-rad wrote:I don't think raising your fuel pressure by even a few lbs will increase injector flow significantly. You either need bigger injectors running at standard duty cycle or change fuel computer.

To avoid any misunderstandings: (maybe my choice of words is just bad - sorry

)

Engine/car is currently running with original Bosch AFM that came with the 75/Milano 3.0l we installed.

The larger BMW 535i AFM is just a mod as describes here: http://www.alfagtv6.com/afm_mods.htm

Now when you add more air to an engine you have to add more fuel to get it to rev properly, right?

Therefore an adjustable fuel pressure regulator...

But at the same time I won't the rev-limiter moved up because an engine with fastroad cams needs more revs to perform more bhp whilst it also lacks torque below 4000 rpm, right? And a 5700 cut off is WAY to early...

Several Alfa-mechanics told me that this engine easily does 7000 rpm without any concerns...

I'm not sure whether to push the limiter THAT far though, but 6500 it should at least do!

x-rad · Post by **x-rad** » Tue Aug 21, 2007 2:35 pm

which will be about zero increase at full throttle if Fuel pressure reg is working correctly and If stock fuel pressure is only 42lbs as output by the pump..

Basically, if the stock fuel pump puts out say 50-55 lbs, then putting on an adjustable regulator will benefit you...but only minimally as you are at the edge of injector performance anyway

I would get a set of slightly higher flow injectors and an adjustable fuel pressure regulator

CBox: my ECU is same as yours 3.0

My Igniton box is different! 0 227 921 001 from 2.5 GTV6 harness. I have not hit any rev limit with my 'fixed' ecu and the 2.5 ign modules (i have tried one from ajunk yard and my original one. I doubt there is a rev limiter in my ignition modules as I have had the needle beyond 7500.

Changing harnesses is probably not an option for you so maybe go with stand alone...will solve all the above problems..except for cost

Cboxoak · Post by **Cboxoak** » Wed Aug 22, 2007 9:50 am

Aha... So what you are basically telling me is that an adjustable FPR is a waste of money?? That is ofcourse, if the original can deliever enough fuel..?

I have a 2.5 fuel ecu (0 280 001 117) so what I really need to get hold on is an ignition box also from a 2.5 if I wan't NO rev liniter..?

The way I see it that would be the easiest solution! Correct me if I'm wrong..?

A 3.0l runs fine on both 2.5 ecu, and ignition box?

x-rad · Post by **x-rad** » Wed Aug 22, 2007 12:38 pm

OK: you have to answer this question:.. Which wiring harness do you have and is it in gtv6?

IF you have a 3.0 engine..you want to use the 3.0 ECU and the GTV6 spark control on a gtv6 harness.

3.0 ECU is specific to the 3.0engine in terms of fuel delivery...especially if you have a 3.0 with more air at higher rpms...you will run lean even with TPS at full.

3.0 or 2.5 Milano spark box is totally different than 2.5 GTV6 spark box, so that you can't just plug new box into old GTV6 harness and v/v.

Also, you will want to make the resistor change in the 3.0ECU as previously discussed

I am not sure if rev limiters are "country of Destination" specific...meaning Bosch may have built Country specific components

Cboxoak · Post by **Cboxoak** » Wed Aug 22, 2007 1:03 pm

The wiring is from a 3.0 75/Milano

I have the same looking boxes (different number though) as the one in top left and bottom so a 2.5 ign. box won't fit my wiring I see...

But thanx for all your help

x-rad · Post by **x-rad** » Wed Aug 22, 2007 4:58 pm

Yep....no problem

As others have stated...Milano Ign box probably has rev limiter.... but I don't have it hooked up to to say one way or the other...

Cboxoak · Post by **Cboxoak** » Thu Sep 06, 2007 12:19 pm

UPDATE:

I can now for SURE confirm that the Alfa 3.0 V6 with Jetronic setup has rev-limiter in BOTH ignition box and fuel ECU.

I got my ECU modified a couple of days ago (as described in another thread) and it moved the fuel limiter but still the igniton box cuts the spark @ 6300 rpm (app) so I got an improvement at about 5-600 rpm...

My fuel ECU had a resistor from stock with 6.6K ohm that made fuel cut off @ 5700 - NOW we put in 2.2K ohm to ensure it will rev beyond 7000 rpm when I get my ign.box modified.

So next step is to modify the ignition box. More to follow...

x-rad · Post by **x-rad** » Thu Sep 06, 2007 4:25 pm

Cbox: tell us what you modify in the ign box when you do the surgery..