Peugeot 1.9 8V GTi - setting up the modified engine

[DamirGTI]

Hi Guy !

Please can you diagnose these spark plugs for me ? engine is Peugeot 1.9 8v XU9JA non CAT ..

The reason im asking this is because i have raise compression ratio from 9.6 to 11.1 with flat top pistons and engine now detonate on factory ignition timing . I've set timing now almost to the end beyond 5 degree and it is ok. detonate only in 4-th or 5-th on full load started from 2000rpm in these two gears on 98 octane gas , but idle speed is now bad which i can't adjust revs jumping all over from 700rmp to 1000-1200rmp ..
What can you recommend :
1)Mappable ignition (how can i do this ? i have Bosch distributor with vacuum advance standard on my engine)

2)Can i modify this factory distributor ? if so how ?

3)Colder plugs ( if so how much colder ? i have now NGK BCP6E and try to change them today with new set of NGK BCPR7ES one step colder..)

4)Buy adjustable camshaft pulley and retard the camshaft

5)Richen the mixture (is it advisable to do this on Air-Flow Sensor potentiometer ? - loosen the tension of the spring by one teeth or two )

6) something else maybe ?

I'm in real trouble here i can't take the car to rolling road to adjust this properly because we don't have these in my country .. maybe just one Dastek dyno to far from where i live but they do only chip tuning so not much help from them .. Only Bosch service has left for adjusting Air-Fuel ratio as option ..

Also I¢ž¢ve fit modified head (if you remember me posting that here on your site)on that engine with high compression pistons so the mixture was a little lean me thinks , spark plugs was white to light grey before i richen the mixture on AFM potentiometer

Engine temperature is good from 70 to 75 max 80 degree when driving and it dosn't overheat even when i use it really hard .

Please help , i don't want to destroy this engine ! and i'm tottaly on my own with all this ..

Thanks
Damir

[Guy Croft]

Damir, hi. First read:

http://guy-croft.com/viewtopic.php?t=268


Is the injection Bosch L/LE type or K? If L you need to raise the fuel delivery pressure to enrich the mixture, you should not attempt alterations to the flowmeter/mixture screw. This may solve the problem - if you are lucky. Set the ignition timing to std setting, blank off the vacuum advance and use the 7 grade plugs.

You need to get a 0-50 psi fuel pressure gauge in the inlet manifold fuel rail, make a note of the fuel delivery pressure at idle. Fit an adjustable fuel pressure regulator and increase the idle delivery pressure by 5 psi. Set the enrichment screw to give factory CO emission at idle - without cat I imagine 2.5-3.5% CO. You need a proper gas analyser to do that. Then road test with that and see if it improves the engine. You can raise it higher if need be but in my exp 7psi is about the limit. i have done this, it may work.

Report back when you have done this. I would like to see a photo of the air flow meter system, to be honest I don't know what is fitted on that unit.

GC

[DamirGTI]

Hi !

Injection type is early Bosch LE-Jetronic so it has ECU , Air-Flow Sensor , Throttle Position Sensor , Themperature Sensor (one in cooling system and one in Air-Flow Sensor inside..) and Supplementary Air Device .

I've blanked the vacuum advance hose allready but i didn't try to move timming back to factory settings with this new plugs - i will try to do that .

Ok. but can this rasing fuel pressure be dangerous ? could this lead to bore wash or overfuleling in engine ?
First I must order that pressure regulator from your country , as i can't buy that gauge here in Coatia !!
I will contact you for sure when i buy this pressure reglator .

Thanks
Damir

And requested pictures of Air-Flow Sensor :

[Guy Croft]

I_don't_give_dangerous_advice!

What I suggest is one of the few (possible) ways of dealing with what I suspect is a over-lean fuelling problem.

I don't trade in these things, contact these people:

http://www.fuelsystem.co.uk


GC

[DamirGTI]

Ok !

The reason i did mention that is because i've read some posts on other forums about this fule pressure valve where people are sayin something about bore wash overfuleing but that was the case when fitting this pressure valves on standar engines , any way no matter ..

I belewe you !!

Thanks for link
Damir

[Guy Croft]

Damir, hi

for your info and for the general enlightenment of other readers:

You are not the first to do head mods and then wonder why the engine detonates! I see this all the time. As I often say, if people - you incl read more about the effects (eg: here) before undertaking mods it would be much better.

What you've done is make mods that (and I did not do the head so I am guessing) that have increased the airflow. I keep saying (and I guess I'll have to keep saying) 'don't expect the fuel injection system to be able to cope with the increased airflow'. It may not. The cylinders will pump more air if you let them but it does not follow (even with carbs to an extent) that the fuel system will be able to deliver enough gasoline to balance the A/F ratio. There is only one FI system that has any chance of doing that and that is Bosch K, certainly not L.

If the engine is detonating it is usually one of several causes:
1. Fuel octane too low (you have told me 98RON which should be fine)
2. Ignition timing over advanced
3. Too hot (yours is not overheating)
4. Way_too-lean. In other words - the most likely cause in your case.

By raising the fuel delivery pressure by the modest percentage I have indicated there is a reasonable chance that a good A/F ratio will be restored. If it cannot be done that way you're in real trouble, because that airflow meter may have to be replaced by a mappable ecu and the whole unit recalibrated from scratch.

For what it is worth: I don't like to see people struggling as you are, no ho. But I cannot warn everyone personally - who starts modifying heads - about the end result of what they are doing - unless they ask me before they start. There are enough GC 'warnings' on this site but they are only any use if people bother to read them. The sad reality seems to be that like on other forums folks only head for their own topic and read little else, never use the search, never print off threads and keep them for reference.. this is why the same old stuff gets posted over and over.

GC

[TR-Spider]

Hi Damir

just a small additional note:
in order to be able to detect wether your car runs too lean or not, you should have a Lambda-meter on board which shows you the mixture at driving conditions (acceleration, full load etc.). Otherwise, if you have to rely on spark plugs only, I am afraid you will be lost.

Now there are two kinds of Lambda-meters,
the cheap one which runs with a standard lambda probe (use a new one, with heating aprox. 50 euros) with some Voltmeter, or more priactical some selfmade LED indicator (blueprints from internet, material aprox. 10 euros). This can already show you if you run too rich or too lean and in which directions your modifications go. I think it is a sufficient tool to get the basic adjustments right on a normaly aspirated engine, at least it was for me when I fiddled with my L-Jetronic.

However, for more accurate tuning you should use a Wideband Lambda-meter, which is more accurate from design (its a small chemical factory, really) and has (a the name indicates) a wide indicating band in the interessting range from Lambda 0.8 to 1.2 . Unfortunately these ones are expensive at aprox 500 euros.

Guy, I do admire your patience and dedication running this great forum and keeping it at such good level aside your daily buisiness!

Thomas

[DamirGTI]

Hi!

Yes its true and i understadnd all this you have sad as people often venture too far with these things and they think that ti will be ok. just to put high flowed head and maybe a chip to raise fuel ratio a little (wich is stupid me thinks..) without all other real modifications on fuel system , ignition , cooling ..because this is essential thing to do when making some serious modifications on standard engine with standard fuel - ingnition system , and all this engine modificatons dosn't work as a single items but always in combination of a few things together and with need for adjusting fuel ignition timming and all other things to bring the power up... often all that cost so much that it's not worth for somebody who use that car as daily drive .
I was expecting this fuel-detonation problems when i start to build this moded engine but i didn't know how high gains can i expect in air flow and compression ratio with all this , so i think that it was a experimental engine to me that i can see what i can build (my first time doing this!) and how it will perform with this mods .

The major problem to me is that i really can't find anybody to help me with all this things , local mechanics usualy know much less than me about all this engine modification things , and other i can't buy anything in this stupid country except spoylers and rims .. even dcecnt special hand or mesuring tools is a real lootery to find here !
Any way i'm no good with these fuel-electric stuf on cars also can't find anybody trusted who will know what to do with this and do this properly on dyno.
So i'm trying to learn to repair car mechanic , electric , suspension , bodywork and everything inside and outside the car by myself !

Damir

[DamirGTI]

Hi Thomas !

Been thinking about that air-fuel gauge , but as you have sad i don't know how acurate these simple cheap gagues are ?!
Wide band lambda meters are a little too expencive for me as amateur !

Damir

[Guy Croft]

Damir hi,

welcome - that is how I started! Got very little help from anyone, had to teach myself. I cannot say that having a degree helped me overmuch in the beginning. Be careful - you might end up being good at it and doing for a living. Sounds like you could do with some experts there..

Anyhow, in the meantime - keep following the advice here and you have a good chance of ending up with a super engine. Get the right tools and equipment, don't take chances. To be a successful race engine builder you must trust your instincts - is something looks wrong - it probably is.

GC

[DamirGTI]

Hi Guy !

Thanks for thiniking like that , you are of great help to me !

Well i read some engine tuning books (on english language !) , i'm on few other car forums and i'm working on my car almost every day now , a little bit of reading and then i go and try to do that on my car thats how i teach myself , sometimes i go for work in local car mechanic workshop just to see all other types of cars how they look under the boonet what diferences are between them in mechanical parts and all other things ..

Damir

[TR-Spider]

Hi Damir

as I said, the cheap Lambdameter was accurate enough for me to tune my L-Jetronic.

The important things are
use a new Lanbda probe (they foul with age and use)
calibrate your LED display carefully with a proper digital Voltmeter (or use directly a Voltmeter which your copilot reads).

Typically with a cheap narrowband Lambdameter you use 10 LEDs from 0.1 to 1.0 Volts, where 0.5 Volts is Lambda=1.
Using different coulors LED helps like
0.1 to0.4 Volts =too lean
0.5 to 0.7= OK and
0.8 to 1.0 is too rich.

I personally tried to adjust to 0.7 to be on the save and powerfull side.

You will need several iterations with
increasing the fuel pressure to get the necessary fuel at max airflow, testdrive
adjusting the spring slightly to shift the fuel along the rev-band (to correct for example too rich at low rpm=>spring harder), testdrive
adjusting idle again...and so on.

In the beginning only change one thing at the time, so you get a feeling on what is happening under your bonnet. And do some sort of marking/bookkeeping on what you changed, in order to be able to go back if you went wrong.

During static conditions like acellerating 3rd gear uphill or 4th / 5th gear topspeed on the highway you should see enough. I myself did most of these adjustment drives at night, little traffic and better to see the LEDs. Helps if you use the same roads all the time
But please be carefull and keep one eye on the road...

Thomas

[DamirGTI]

Hi Thomas !

Intresting , i will try that thanks for info !

Damir

[benlilly]

Hi Damir,

I have been giving all the above issues some thought since you started this post as I predict I will experience similar problems when my Peugeot 205 8V engine is complete.

As I think Guy has already mentioned in this thread, and the thread on engine modifications working with OE injection systems, rasing the fuel pressure can help to solve underfuelling due to increased air flow but with the Bosch L-Jetronic this can also result in over fueling at lower rpm where the flap position still controls fueling

Guy mentioned some time ago about using a rising rate fuel pressure regulator (controlled by manifold pressure) on applications such as yours. Whilst searching for similar products I came across a US company who make one of these and is fully adjustable for rate of fuel pressure increase and onset of increase. This could be a very elegant solution as it would eliminate the need to adjust the air meter spring tension. They cost approximately 200 euros.

Here is their website:
http://www.cartech.net/fmu2020.htm

I haven't used one of these so obviously can't confirm quality of results.

Ben

[DamirGTI]

Hi Ben !

I've made my engine with flat top pistons from 1.9 DFZ (205 cabrio CTi) they are like 1.6 type pistons , its easier to fit them because you don't have to swap conrods from 1.9 to 1.6 pistons . I use these pistons togheader with liners from that DFZ engine .
Head is ported with 4 angle seats for exhaust (15, 45, 60, 75) and 5 angle for inlet (15, 30,45, 60, 75) my mate made them with Neway tools . Gearbox is also changed and its from Peugeot 405 2.0 SRi engine now .
Allthou i've made onley 500 miles from complete rebuild i can notice that it has facinating low end torque and its pulling much harder in all gears than ever before (i didn't rev it past 4000-4500rmp yet !) i'm really satisfied with this engine but i think that it can make even more power if i do something about this fuel and ignition timing . I'm really short budget with this so i must be creative in buying these fuel - ingnition components !

Carbs or Throttle bodies with mappable ignition will be great for this engine me thinks , but this cost so much and can't aford it ..

Thanks for link !
Damir