Lars

I have installed my Dawes Air/Fuel Ratio Meter in a standard MY99. Before installation I have adjusted the Dawes AFR to
Red 600 to 830 mV
Yellow 830 to 879 mV
Green 879 o 920 mV
Blue 920 to 1000 mV

On a standard car with full boost 0.92bar - 13.5 PSI I get yellow light.
With Dawes MBC installed ( 1mm bleed hole ) and adjusted to 1.05 bar - 15 PSI I get under full boost yellow light up to 3.800 rev. and then it change to green, it stay green all the way to 6.500 rev. I'm able to run full boost 15PSI in 2, 3 an 4 gear, all the way up to 6500rev, if I put load on the car, either by going steep uphill or left foot braking. If you do not put load on the car it will drop in boóst in high rev.
With standard solonoide boost control my boost peak at 1 bar-14,5 PSi and then drop to 13,5 PSI. This adjustment is gone with the Dawes, it go to 15 PSI and stay rock stable, I think this is due to shorter hose used with Dawes.
Regards Lars

catflap

Im thinking of geting the daws thing along with the A/F box.

How much differene would it make to a standard MY99 with decat centre and back box?

If it worth the 100 quid or so its gona cost me?

john banks

Dawes was only about £26 on a group buy including all postage.

I reckon it can give you about 15% increase in peak power, more in the midrange depending on how you set it. I got less on my car as I already was running higher boost because of PPP and the effects of a downpipe. PPP ECU lets you run a bit higher (say 18 vs 16 PSI) because of higher fuel cut.

A Dawes would give you a similar real world improvement to a PPP car - you may run slightly less midrange boost (16 vs 17PSI) but spool up, and the top end power make up for it. For 1.5% of the price.

I am working on a DIY electronic boost controller, but honestly don't think I will achieve any performance or safety improvement.

catflap

interesting, to for a little dosh the car could see a nice improvement.

After i get my springs done ill go ahed and get it.

Or saee if i can get another group by runing, who did the last one?

john banks

Luke (Deacon).

Lars

Thanks for advise John. The dawes AFR is similar to the DIY AFR you are building. Chip usen in Dawes AFR is LM3914, It's easy to open and to locate the two adjustment potentiometers for Max and min ref voltages. You just need to have some accurate measurement device, to set it up as you want. It is nice looking and i have installed it in the ashtray size is 5 x 3x 1 cm.
I try to change the adjustment to your recommendation, as I want to use the blue LED, as is it never light up.

I have tested a bit more on max boost. In 3 gear WOT and left foot braking I have 1.05 bar and after 6000 rev it is dropping to 0.9 bar.
I'm looking forward to a trip on the German autobahn and try the top speed. As totally standard I have measured it to 242 KM/t with a garmin GPS ( do not know what this is in miles.
Lars

Lars

Correction, sorry in my first post there was a typing error. My AFR is adjusted to

Red 600 to 830 mV
Yellow 830 to 870 mV ( NOT 879mV)
Green 870 to 920 mV
Blue 920 to 1000 mV

Lars

john banks

So have you Scott - look at the posting times and dates if that is what you are meaning. Puzzled.

T-uk

I think it is something to do with edited messages

R.B.5

On an MY99 what colour wire or where is the correct oxygen wire to tap of located on the ecu??

Thx lads

Devil's Refugee

John,

Would be interested in your DIY project.
Does this affect any Tek remaps/ Dawes installation or will it work in conjunction with the Tek3 ?

mega_stream

Quick question, still on topic though...

When you talk about 16-17psi, do you mean this is the value that is kept on WOT in say 4th or 5th, or the value that the boost peaks at momentarily?

Is the Dawes sposed to be set up using the reading the boost needle stays at or the one it swings to before settling down?

Scott.T

iTrader: (2)

Devil's Refugee,

Here's a layout for the DIY project.....
I think someone has my layoout and more info on a web-site somewhere....


Here's my original 10 LED version (alot more tricky to fit in such a small box)



Somewhere on here is the original thread, but I can't seem to find it at the moment :

Parts....
Farnell Pt.No / Description / Price
332489 / Red LED / 15p
332507 / Yellow LED / 11p
332509 / Green LED / 12p
614671 / 4K7 Pot / 17p
3557078 / LM3914N-1 / £2.67

A suitable plastic box for about £1.00 and some Stripboard.

john banks

Theo the circuit works great with any ECU.

Most PPP are between 15 and 16 some a bit higher - but they peak a lot in the cold.

With the Dawes I never get any peaks. But held boost is the value it settles to in the midrange after any quick initial peak. So the value it settles to in 5th gear by 4000 RPM is held boost.

john banks

Red 600 to 830 mV
Yellow 830 to 879 mV
Green 879 o 920 mV
Blue 920 to 1000 mV

That is better than it comes as standard, but in my opinion your yellow and green ranges are way too wide and you may want to use all four lights to get better resolution and more useful information if you are only using it on full boost. 830mV represents about 4% CO 880mV represents about 8% CO. So at WOT you are not really using the first and the last lights, and with the yellow light on at WOT you could be ideally rich or getting quite seriously lean and not know. The absence of a green light doesn't tell you that you are too lean either - you could be 7-8% for example and because your green light is not lit you could be worried that you might be as low as 4% and not really know. At the end of the day you want a gauge that tells you if you are lean at WOT. Your gauge will not tell the difference between ideal and quite seriously lean IMHO. Can it be adjusted any more? To be useful and give you goo resolution this would be better I think.

mV %CO AFR

<600 <1% >15:1
720 1% 14:1
760 2%
800 3%
840 5% 13:1
860 6% 12:1
880 >8% 11:1

[Edited by john banks - 1/11/2002 4:25:13 PM]

john banks

If you are only measuring at WOT how about:

810-830
830-850
850-870
870-890

If you are any richer than the top light there is not much you can do about it unless you buy an ECU or fuel computer. If you are not on the top two lights at WOT/full boost lift off and panic. You will also benefit from less distracting flashing at stoich if you increase the bottom one.

The speed you mentioned is 150mph.

Adjustments will depend on what pins of the LM3914 that have been connected and whether it is a LM3914N or not. A dot usually marks pin one at the bottom left as you look from the top of the chip. Pin 1 is LED 1, the pin diagonally opposite is LED 10. Depending on what pins the four LEDs are connected two you may not get the exact ranges you want.

[Edited by john banks - 1/12/2002 11:11:58 AM]

Scott.T

iTrader: (2)

Good choice of values John. I think I may set my AFR up to those. As u know mine is set to run from 720mV to 900mV at the mo'.

If it's it the ashtray (like mine), distracting stoich is easily remeded...just close it...

I see you've been time travelling again then John...

[Edited by Scott.T - 1/12/2002 5:34:38 PM]

Scott.T

iTrader: (2)

Strange...that said Jan 12th just now....
Or is it something to do with post '666'

[Edited by Scott.T - 1/13/2002 9:41:51 AM]