[Gmecm] 7730 Maximum RPM limit

[Darren Freed]

What, specifically, do you want to do?  Extend tables?  If simply rev limit, that is based on a 2 byte value (ref period).  I've run my 3400DOHC up to 7500 rpm with a '7730 and also with a '6401 (sefi, which, btw, stays sefi all the way up, verified on the pcm bench) with no difficulty - ie the ecm didn't take a big dump.

darren



----- Original Message -----
From: Ryan Hess <rgmecm at yahoo.com>
Date: Tuesday, April 18, 2006 10:34 am
Subject: Re: [Gmecm] 7730 Maximum RPM limit

> Welp, I wrote a QBasic program to pulse the parallel port, and 
> hooked my laptop directly to the computer in car.  I tried taking 
> some datalogs with tunerpro RT and freescan, and both have 
> confirmed the findings...  It appears as though RPM/25 is directly 
> reported via the ALDL stream.  It is sent as a single byte, which 
> means that at a maximum of 255, the reported rpm value is 6375.  
> This is where it apparently maxes out.  I'm kind of surprised I 
> hadn't noticed this before, but I guess the amount of time I spend 
> above 6375 is minimal and close to my revlimiter, so....
> 
> I guess my next question is, how much work (ha!) would it be to 
> turn RPM/25 into a 2 byte value?  Or...  would it be even simpler 
> to change the rpm/25 measuring routine into an rpm/35 or 40??  
> What kind of complications am I looking at here?  Thanks all,
> 
> Ryan
> 
> 
> Ryan Hess <rgmecm at yahoo.com> wrote: Interesting.  If that's true, 
> I wonder if I can cut out unnecessary function calls (EGR, CCP, 
> air injection, whatever else I can find) to increase that...  What 
> is the failure mode when this limit is reached?  Does it just act 
> like a revlimiter, or crash, or ??  Thanks btw...  it does help.
> 
> Ryan
> 
> Bill Shaw  wrote: Don't know for sure (which is why I kept my 
> mouth shut!) but I seem to
> remember reading about 7300 being the limit due to processing speed.
> 
> let us know what you find on the bench :-)
> 
> Bill
> 
> > From: Ryan Hess 
> > Reply-To: gmecm at diy-efi.org
> > Date: Mon, 17 Apr 2006 16:03:17 -0700 (PDT)
> > To: gmecm at diy-efi.org
> > Subject: Re: [Gmecm] 7730 Maximum RPM limit
> > 
> > I guess I'll have to build a test bench and find out myself, eh? 
> Or are you
> > guys always this slow in replying? :-p
> > 
> > Ryan
> > 
> > Ryan Hess  wrote: Hi again,
> > 
> > I'm currently running a northstar on a 7730, using the DIS $a1.  
> Currently I
> > have the revlimit set to 6500, and it works great, I've hit  it 
> occasionally.> However, I will be upgrading  to some better heads 
> soon, which will allow me
> > to rev even higher  without valve float.  7500 seems to be the 
> magic number.
> > After a rebuilt bottom end (I don't know for sure if I'd go this 
> far...  but
> > want to leave my options open), 8500 would be possible.  Now,  
> after reading
> > about LT1 computers hiccupping at high rpm, my question  is- has 
> anyone ever
> > tested the "max rpm" the 7730 can handle and/or  have any 
> guesstimates?  How
> > does processor speed compare to other  aftermarket ECM's capable 
> of high RPM?
> > (eg holley, haltec,  etc)  I assume they run faster processors 
> with more
> > bloated  compiled code, so I wonder if they're in the same place 
> "speed wise".
> > 
> > Ryan
> > 
> > 
> > 
> > ---------------------------------
> > How low will we go? Check out Yahoo! Messenger???s low  PC-to-
> Phone call
> > rates.
> > _______________________________________________
> > Gmecm mailing list
> > Gmecm at diy-efi.org
> > http://lists.diy-efi.org/mailman/listinfo/gmecm
> > 
> > 
> > 
> > ---------------------------------
> > How low will we go? Check out Yahoo! Messenger???s low  PC-to-
> Phone call rates.
> > _______________________________________________
> > Gmecm mailing list
> > Gmecm at diy-efi.org
> > http://lists.diy-efi.org/mailman/listinfo/gmecm
> 
> _______________________________________________
> Gmecm mailing list
> Gmecm at diy-efi.org
> http://lists.diy-efi.org/mailman/listinfo/gmecm
> 
> 
>  
> ---------------------------------
> Blab-away for as little as 1???/min. Make  PC-to-Phone Calls using 
> Yahoo! Messenger with Voice.
> _______________________________________________
> Gmecm mailing list
> Gmecm at diy-efi.org
> http://lists.diy-efi.org/mailman/listinfo/gmecm
> 
> 
>                	
> ---------------------------------
> Yahoo! Messenger with Voice. PC-to-Phone calls for ridiculously 
> low rates.
> _______________________________________________
> Gmecm mailing list
> Gmecm at diy-efi.org
> http://lists.diy-efi.org/mailman/listinfo/gmecm
>