Discussion in '16-valve' started by barny, Oct 14, 2006.
Oh ballcocks - 2 secs, I'll check that info
Bingo, so what I put above would make sense:
4.608/4.194304 = 1.099
7200 * 1.099 = 7912.something which agrees with your 7900, Chris.
So just choose your crystal that way.
Farnell UK part number for a C-MAC 4.608MHz part is 9712836.
The next common frequency up from that appears to be 4.9152MHz which would correspond to 8437RPM. And so on. "Scrreeeeeeeeeeeeee....bang"
How does the ecu determine what ignition values to give above the stock limiter?
Nice to have that info up here Trev - spot on.
G - when you say ignition values, do you mean the stock rev limit?
Glad to see this has been brought back to the table. Im getting my hands on a new block that im going to have tuned for high revs, ie, balanced and knife edged crank, etc. I really want to raise the limit on mine, and if I could get my hands on one of these crystals Id put it in right away. unfortunately, I cant find a crystal of this type in the USA.
dont suppose I could talk anyone into picking one up and shiping it to me in the USA could I?
I use Farnell a fair bit, so could get one for you next time I make an order and send it over for you. But I would have thought that you could get this crystal from Digi-Key, to be honest, who appear to have an even bigger range of stuff than Farnell do, and Digi-Key are over in your part of the world (though they're now also fully set up to ship to the UK). I'll have a look at Digi-key later today.
Well, the thing is, the ignition map will have been 'stretched'.
Think of it this way: we're speeding up the clock to the microprocessor inside the ECU. So, in layman's terms, think of it this way: to the ECU, the engine is appearing to run at a slower speed than it actually is. When the ECU thinks that it's going at 7200 and applies the limit, it's actually at 7900.
Negative side effect is that any other timing parameters are also distorted by the same factor.
I tried digikey and mouser, but neither of them have this specific frequency crystal. the only place I can get that specific crystal is from uk sources. (farnell)
Do you think any 4.608mhz cystel would work?
Order the part number I quoted above (9712836) from Farnell. Only 79p!
Yes you could use any 4.608MHz crystal but it needs to be in a HC49 package (in other words, looks identical to the original one on the board, so that it can solder directly in its place).
Found this on ebay, i couldent get on the Farnell website.
That'll do it.
hi trev your very knowledgable, im doing and elecrtical engineering course but only jsut started and all of this does sort of make sense other thatn finding the factors to give you the gain on the new crystal/limit.
so what your sayin is replace the old crystal and solder on and you have a higher limit on the 16v........barny says it looses lower down torque is this right?
i have 3 16v ecu so i could jsut swap and take out for drive see if really does make any difference?
Hmmm, that's what I thought you were saying.
So as we all know, if you run 95ron in a KR it det's in the mid range unless you retard the static timing (alternately run 97/8ron and it's fine). Advance the timing whilst running 98ron and you get more top power but your back into dealing with the mid range det.
So I'm wondering if applying this mod would help - The ECU thinks engine is slower so would use less advance for a given rpm, maybe you could advance the static timing (running 97/8ron) and be "through" the mid range det area whilst still at a lower advance value...?
i.e. the advance curve has not changed it's just spread over a wider range, so the "det area" may now be seeing a lower advance value allowing more static timing thus giving more advance at the top end?
If what Trev is saying is correct (and I think he is) then the torque loss would be because it's running less advance, hence my thoughts above
This is starting to go a little over my head.
As i use my 1.8 16V KR for racing i wanted to have more revs but i don't wana lose any torque. i only use V-power.
So do we know how the car will be after the crysle change on my set up (after a RR tune)?
not sure will have to test basically.......if i can dig out ecu's and order some crystals then maybe we'll find out.......ill try and get ontop of this asap
The change expands the timing over the new bigger range (probably) resulting in less advance (until max rpm) which will reduce torque. However, advancing the static timing (i.e. spin the dizzy at tick-over) may equal or even exceed the original advance/torque
As 87_UMN has said, we don't until someone tries it
has anyone tried this yet ?
I would like to know the results.
SOrry to fetch up an old thread, I have a Gti 8v MK2 and was wonndering would this method work on it??
very interesting post
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