Race Engine Forum UK

Hello,
YOu might try to use Megasquirt EFI, this is cheap and working very good but you will need to map it by yourself.
Tomasz

A word about 8V ignition timing and AFR's.

Advance Curve
First of all, there is way too much advance down low in the std. 205 GTi curve for anything over 9.5:1. You will still need 31-32 deg. of total advance over 4000 to make maximum power, even with 11:1. What you're probably doing is curing the 2000-3000 range pinging by retarding the overall timing, at the expense of top end power. You need to either fit stronger springs in the distributor advance, or fit mapped ignition.

AFR's
I have both wide and narrow band sensors to check AFR's. Stoichmetric, 14.7:1 is equal to 0.638V on a typical narrow band sensor, not 0.5V. I have cross checked voltages against an M&W Uego and Haltech Uego and found the following of typical NTK and Bosch narrow band sensors.

0.78V - 13.5:1
0.82V - 13:1
0.85V - 12.7:1

A cat. and lamda equipped 205 stays between 0.6V and 0.9V under ALL conditions, except on overrun.

The best way to check AFR voltages cheaply is with an old analoque multimeter and a narrow band sensor. Digital multimeters read too fast. Failing that, buy a 0-1V panel meter. If not that, a 0-1mA panel meter and put a 100Kohm trimpot in series with it. Calibrate the meter off a known low voltage output (flat AA cell) so it reads 1V at full scale deflection.

Go for a drive and aim to keep the full load voltage between 0.8 and 0.9V. Anything less than 0.8V is too lean at full load.

MODEL POST!

Peter, hi

well done indeed, a most informative and useful post, just the kind of thing I like to see here - thank you!

GC

Hi !

Yes , nice one Peter thanks !

Just how can i replace this springs in distributor ? and where to buy these ?
Yes i have been altering ignition timming when it was started to pink around 2000 and 3000rmp mostley in 4-th and 5-th gear , and this was the onley time i can hear it pinking ..

I don't have lambda sensor OE in my car so i must buy this sensor first and find the best place for fit in exhaust system .
What cind of sensor should i buy ? is narrow band sensor like normal lambda sensor for CAT cars or not ? i've been in car parts store and they have this lambda sensors with 2 , 4 and 8 wire output .. i don't know which one should i buy ..

Thanks
Damir

Not many people regraph distributors these days. You'll need to find someone with grey hair and glasses for a start! Start ringing around. If it were over here I could help you.

A four wire sensor will be most usefull. The two white wires are the heating element (+12V and GND), black is signal +ve, grey signal -ve. You can run without the heating element if very close to the motor.

The best thing to do is make a pipe to stick in your tailpipe. It needs to be approx. 25mm diameter and 500 long. The sensor must be perpendicular to flow and half way along the pipe. It will difficult to sample under 1500 rpm however, due to lack of exhaust flow.

That multimter will be excellent. Set it to the 3V DC scale.

Hi Peter !

Ok. i will try to find somebody who might match that description !
But if i go for mappable ignition how can i make this ? I've heard something about Megajol mappable ignition , also that Megasquirt can be used for ignition system too..
Can i fit complete ignition system from Peugeot 205 Motronic or maybe some other car ? will that work ?

Thanks !
Damir

try these in uk, they have become popular over the last few years,

http://www.h-h-ignitionsolutions.co.uk/

rich

Damir, hi

I advise a lot of people every day. I try to think of solutions that suit them. You have 3 main problems if you keep fuel injection.

1. Recalibration of the OE system is going to be very difficult. I do not think you will succeed. I see you are already considering other systems.
2. Other FI systems are going to cost quite a lot and you have no experience of them at all.
3. You cannot get half the things you need where you live and there is no-one around who can calibrate the engine properly.

My advice now is - fabricate a sidedraft inlet manifold and get a pair of Weber carbs. If you continue to drive this engine in current form you are going to damage it. Give this careful thought. Everyone is trying their best to give you long distance advice and that is great, but it's getting way too complicated for someone of little experience.

GC

Hi !

Yes Guy you're right , mapping ignition or fuel is almost impossible in this country because we don't have dyno for that job and most important you can't find expirianced person who will know to do all this , and really i can't do this mapping job by myself .

Intresting i've been thinking about Weber carbs like good soultion but i'm a little worried about fuel consumption , how much will the increase be with carbs ?

Thanks !
Damir

Damir hi,

oddly enough another client with the same unit just asked me that. i am all for practical advice, here goes: Fuel consumption is totally dependent on how much power the engine develops. That power depends on how hard you press the throttle and what the fuel system consists of.

The fuel distribution (correct amount per cylinder for best A/F ratio) is better with FI. So is the homogeneity of the fuelling - how well the gasoline is mixed with the air.

I don't want to talk about comparisons between FI and carbs, no-one tunes an engine then worries about fuel consumption. Whilst FI engines burn better for same throttle position - they also develop more power at that throttle position - and that means more gasoline, thus it follows a driver who has race injection might need less throttle for a given speed ... all very esoteric really and no-one drives like that makes that comparison. 3% better? No idea. I know of few smaller firms that could measure fuel consumption accurately enough (under real driving conditions) to make the comparison worth reading. You'd have to be Ford to do that and I have seen their facilities for testing it - robot driven cars on rolling roads running for days on computerised test cycles. You can't measure it on a dyno, no ho. You're calibrating to get power and economy is the last thing on your mind, believe me!

You need to draw a distinction between injection systems. I have tested the standard inlet manifold for your motor on the flowbench on modified heads (not unlike yours!) and the flowbench says 'huge loss' of airflow. Put a well sorted sidedraft on the head and the loss disappears and the head becomes capable of over 170bhp on the 1600 unit. Put the OE inlet manifold on with its weird entry shape and I reckon you would be lucky to top 145bhp even with a really good cam.

So with a modified head, I feel bound to ask, 'why modify it and run the OE inlet manifld at all?'. See what I mean? You want throttle bodies? No way, far too costly for the gain you'll get. They are for people competing at National level. Match and flow a good sidedraft manifold from UK's Richard Longman (or someone else who supplies them) and fit sidedraft 40 or 45 DCOE carbs and then the numbers make sense - your engine stops 'knocking', pulls like a train, sounds great and you begin to get the power you were hoping for. And you learn how to jet them here and save a fortune on FI bits and pieces and don't wreck your motor!

If you want economy - drive slowly.

GC

Hi Guy !

What confiuses me is that people often speak - if you junk fuel injection and fit carbs you'r car will drink more fuel ..

Anyway , from now i'm starting to save some money and go for carburetor conversion ! it will be nice to get rid of all this anoying injection sensors also .
Should i buy new carburetors or maybe find some in scrapyard ? also must these carbs be made specially for my engine or are they made to fit on all engines but with different carb to head mainfold for each application ?

Thanks !
Damir

AFR's
I have both wide and narrow band sensors to check AFR's. Stoichmetric, 14.7:1 is equal to 0.638V on a typical narrow band sensor, not 0.5V. I have cross checked voltages against an M&W Uego and Haltech Uego and found the following of typical NTK and Bosch narrow band sensors.

0.78V - 13.5:1
0.82V - 13:1
0.85V - 12.7:1

Peter, that back to back test is real valuable information, thanks.
May I suggest that you publish it in a separate post called "comparison of wideband vs narrowband lambda-meter", that would help finding it again.

Thomas

Hi !

I've been reading and familirise myself about this carburetors , but i don't know for which size should i go 40's or 45's ? i think that 40's will be better on mild modified engine and for mid range power and 45's for highly tuned engine and high revs ..

Damir

Yes, 40 DCOE would be fine, 34mm chokes, rest of the jetting I can advise when you have them, see view of carbs at:

http://www.webcon.co.uk/weber/40dcoe.htm

With second-hand carbs you have to see_before_you_buy or you can end up wasting your money completely. You must also be aware that when you buy carbs they are rarely jetted and choked right for you engine, you must allow for changing most of them.

GC

Hello !

I have some mixture reading , i've bought lambda sensor today (4 wire NGK zirconia sensor) fit him in exhaust system and wire everything up .

Readings are as follows :
0.85 to 0.90v - on crusing (2000rpm)
around steady 0.80V - on mid range (4000rpm)
0.78 to 0.82 - on full load (6000rmp)

So this indicate rich mixture ?! i don't understand why the sprak plugs are white coloured ? can it be because of lead additive ?(i'm putting a little bit of lead additive every time when filling with gas..) or its because the high temp. in cylinders ?

I decided to use digital multimeter because this one has light illumination and this test was at night .

pics :