Slight Hold Back With New Head Fitted

[wardy18 33 1 Cars]

Hi all,

 

Hopefully someone may have an answer

 

I have now fitted and run my new XU10 8v head on the Ally 1.9 block and it went well, it revs so well BUT after each gear change on full chat today at my 1/4 mile sprint event the engine was holding back slightly for a second or 2 and then clear and go like hell again

 

changing gear at say 7000-7200rpm

 

i was adjusting the timing and mixture all day and got the engine running much better but never cured this slight hold back problem, i found i had to richen it alot with the new head and put this down to the bigger inlets and flowed head etc

 

any thoughts gratefully received

 

regards

 

simon

[wardy18 33 1 Cars]

sitting here thinking it through and I can only think of 3 possible reasons:

 

1 ignition timing

2 fuel pressure

3 carb jetting

 

I'm swaying more towards fueling, ie carbs jetting, only because I started off with the old fuel mixture from the std xu9 head today and this way too lean, each mixture screw was given a good half turn richer which is alot! Could it now be that the carb jetting and choke sizes etc are too small with the bigger valved and flowed XU10 head???

[sutol 0]

sitting here thinking it through and I can only think of 3 possible reasons:

 

1 ignition timing

2 fuel pressure

3 carb jetting

 

I'm swaying more towards fueling, ie carbs jetting, only because I started off with the old fuel mixture from the std xu9 head today and this way too lean, each mixture screw was given a good half turn richer which is alot! Could it now be that the carb jetting and choke sizes etc are too small with the bigger valved and flowed XU10 head???

Either that or port velocities are slowing dramaticaly as you lift off.

Could even be a little too rich at the top end and getting flooded slightly when you lift.

[DamirGTI 342]

I had something similar with my engine

 

Id say it's a combo , fueling + ignition .. stick a WB sensor in the exhaust and take it for a spin (and record the readings - accelerating from part to full throttle ..) , make necessary adjustments with the fueling and then proceed to ignition timing ..

 

Otherwise , it'll never work properly and unleash full power until you tune it up ..

 

Damir

[wardy18 33 1 Cars]

well ive made an unusual discovery when checking the timing with my strobe light. the tdc and btdc marks do not move from where they are at idle rpm to when i rev it right up to 5000rpm or more, its a H&H dizzy i have fitted

 

Sutol has helped me out alot with this and has said that the dizzy should have built in advance and so the advance to maximum when the rpm increases

 

also when trying to base set the dizzy (advancing dizzy until highest rpm is reached then knock it back slightly) the rpm never stops rising before i hit the maximum that i can move the dizzy

 

whats goin on?!

 

has my H&H dizzy packed up?

[wardy18 33 1 Cars]

Oh and i think my carbs settings could be a little off

 

For the 1905cc and a power band up to 6500rpm i should have Choke size 38

 

To work out mains jets to suit its Choke size * 4, so 38 * 4 = 152, so Main Jets 150

 

For Air Corrector Jets it should be Main Jet size + 40, so 150 + 40 = 190

 

Emulsion Tubes should be either F2 or F16, it doesnt make alot of difference apparently

 

So i should be running:

Choke - 38

Mains - 150

Air C - 190

E Tubes - F2 / F16

 

BUT i am running:

Choke - 38

Mains - 145

Air C - 180

E Tubes F16

 

So im running too little Mains and Air Corrector Jets for the size of the chokes!!

 

I have ordered the new Mains and Correctors so will get them fitted and test

 

 

 

Still need to sort the dizzy problems out though

 

Simon

[James_R 3]

throw a 1600 dizzy on to get you going.

 

they do wear out from the revs not too much to get one re-weighed/serviced??

[wardy18 33 1 Cars]

ah ok, wasnt expecting something i paid to be modified to wear out so quick, its not even done 2 seasons of hillclimbs?

[DamirGTI 342]

... scrap the strobe light , adjust the dizzy on the road "by ear" .. but you'll need to sort out the fueling first , then the ignition timing

 

WB sensor would be very helpful during the mixture adjustment , so that you can see weather the engine runs lean or rich on part/full throttle .. or , at least buy an 4 wire zirconia lambda sensor , wire it up , connect it on a digital (or analogue) multimeter and observe the readings while driving ..

 

Damir

[DamirGTI 342]

Out of curiosity , this H&H dizzy , which engine spec did you gave them upon request for redoing advance curve ? from your old engine or this new built one ?!

 

Damir

[wardy18 33 1 Cars]

at least buy an 4 wire zirconia lambda sensor , wire it up , connect it on a digital (or analogue) multimeter and observe the readings while driving ..

 

Damir

 

Hi mate

 

this sounds good, i have a digital multimeter but can you help me get the right "4 wire zirconia lambda sensor" as i've never heard of these and had no idea you could ever fit a multimeter to one to display the readings?! how can this be done?

 

Thanks

[wardy18 33 1 Cars]

Out of curiosity , this H&H dizzy , which engine spec did you gave them upon request for redoing advance curve ? from your old engine or this new built one ?!

 

Damir

 

it was the old engine but all that has changed is that i now have a XU10 8v flowed head on the 1.9 8v ally block so not a massive difference surely?! not enough to need re-curving surely?!

[DamirGTI 342]

Id say that you'll need slight advance curve correction it's head with different cam profile , bigger inlet valves , deeper chambers and as you say it's flowed as well ..

 

CR is now higher too ?

 

As for the zirconia lambda sensor , its std. narrow band sensor (you have choice of one , two , three perhaps , and four wire lambda sensor ) they're fitted to all cat. equipped cars (some of the new , little bit expensive , cars today have factory fitted wideband lambda sensors .. so you can buy one from say WV dealer , but you'll need to fabricate controller to make it work , and a gauge/meter) , the four wire sensor will be best as it has a heating element which will speed up the readings and you don't need to mount it close to the engine .. pop down to your local car part store and ask for “4 wire zirconia lambda sensor” (they're around 40.00 quid .. Bosch , NGK etc.)

 

Then , when you've bought one , you'll need to drill a hole in the exhaust in order to mount it (i drilled the hole just in between the exh. manifold and middle silencer and welded one driveshaft nut on top so that i can screw the sensor in .. thought you can make a “dummy” pipe with sensor fitted and stick it into the tailpipe .. but i prefer the first option for better accuracy ..) and wire it up (instructions will be supplied within the sensor package ..) , there will be two white wires which are the heating element (12v and ground) one black wire (signal +) and one gray wire (signal -) ... connect the white ones as said one on the el. circuit which has 12v with the ignition switched ON , other one on the chassis ground , and the black/grey ones on the multimeter terminals .. set the multimeter on voltage measurement go for a spin and record the voltage readings from the multimeter (but the engine must be warmed up to the working temp. for proper readings) as you'll transfer these voltage readings afterwards into lambda values ..

 

Can find more info here (it might sound complicated now , but it's dead easy once you figure it out !) :

 

http://www.guy-croft.com/viewtopic.php?f=1...ting+up+peugeot

 

Damir

Edited September 6, 2009 by DamirGTI

[boombang 2]

For about a fiver you can get a lambda boss and plus kit from ebay. Better to do this that use a shaft nut, means at any point in the future (assuming you can get it apart!) can check the fuelling by whcaking a sensor in there.

[wardy18 33 1 Cars]

i'm going to re check the whole strobe light timing effort later to see if i can get any results and then if not ill fit a std dizzy back and send mine back to H&H to be re-curved, hoping to go Megajolt over the winter so wont have to put up with this for much longer

 

i do like the sound of this Lambda Sensor idea so ill look into pricing etc

 

thanks for the advice

 

will report back soon

[wardy18 33 1 Cars]

regarding the ignition timing, it might be possible that i have been a helmet and been using Number 1 HT lead for the strobe as the one closest to Cam Belt end, wondering why im well out, only to find that Number 1 cylinder is Flywheel end!! OOPS

 

i also used this side for the Cam timing but luckily the Camshaft Lobes on 1 and 4 are the same, phew, but for ignition purposes 1 will be on firing stroke and 4 wont be causing my strobe lighting to be well out

 

will re-try later

[wardy18 33 1 Cars]

ok ignition timing sorted, it appeared i messed up and was using the wrong ht lead which wasnt on the firing stroke so meant o was 180 deg out!! sorted now and appears that the H&H dizzy has about 15deg built in advance, jus need to find the sweet spot at which full advance at over 4000-5000rpm is at 32deg BTDC

 

new 150 Main Jets and 190 Air Correctors are also on their way so hopefully this will cure my low rpm struggle, called Matt at QEP today to see if he knew about it as he did the head and he said he hasnt much experience with carbs but mentioned that obviously the carbs will need to be much richer as the head is gulping down much more air with the bigger inlet vavles and flowed ports so needs the extra fuel

[wardy18 33 1 Cars]

also asked our Lucas House company, supplier and electrical items etc etc, for a 4 wire Zirconia Lambda Sensor, he looked at me in a very vacant manor!! He quoted me 57 quid for a universal 4 wire lambda sensor, think that a little over priced dont you??

[Saveit 0]

This is exactly what you want mate: Lambda Sensor

Edited September 7, 2009 by Saveit

[DamirGTI 342]

Wideband sensores are way past 57 quid mark (take a look on the ebay) so this'll be your cheapest option , tough you might find universal 4 wire narrow band lambda sensor for a little bit less (depends on brand) but they're all at around 30/40/50 quid (at least over here ..) .. ask on several places for better price ..

 

Anyhow , you won't be able to adjust the fueling properly without the lambda sensor (if decided to do this on your own) as it'll tell you if you need to richen or back off the mixture .. you can't know that without the aid of the lambda sensor , even this narrow band sensor wont be as precise as wideband sensor but it's better than nothing

 

If you can afford one , buy wideband sensor straight away .

 

Damir

[sutol 0]

Wideband sensores are way past 57 quid mark (take a look on the ebay) so this'll be your cheapest option , tough you might find universal 4 wire narrow band lambda sensor for a little bit less (depends on brand) but they're all at around 30/40/50 quid (at least over here ..) .. ask on several places for better price ..

 

Anyhow , you won't be able to adjust the fueling properly without the lambda sensor (if decided to do this on your own) as it'll tell you if you need to richen or back off the mixture .. you can't know that without the aid of the lambda sensor , even this narrow band sensor wont be as precise as wideband sensor but it's better than nothing

 

If you can afford one , buy wideband sensor straight away .

 

Damir

However did we tune Webers or Ignition timing before electonics ?

[DamirGTI 342]

However did we tune Webers or Ignition timing before electonics ?

 

... dunno im not that old ! neither much good with carbs either ..

 

They must have some kind of mixture screws ?! i know is that the high speed jets are fixed (non adjustable) but idle ones are , adjustable ..

 

Never mind , carb vs EFI , he must know weather the engine runs lean or rich , otherwise it might do severe damage to the new built engine .. when he knows what the engine needs , and whats going on inside with air/fuel mixture , then he can decide weather he needs bigger jets , emulsion tubes , chokes etc. etc.

 

Damir

[sutol 0]

... dunno im not that old ! neither much good with carbs either ..

 

They must have some kind of mixture screws ?! i know is that the high speed jets are fixed (non adjustable) but idle ones are , adjustable ..

 

Never mind , carb vs EFI , he must know weather the engine runs lean or rich , otherwise it might do severe damage to the new built engine .. when he knows what the engine needs , and whats going on inside with air/fuel mixture , then he can decide weather he needs bigger jets , emulsion tubes , chokes etc. etc.

 

Damir

We changed tubes/jets until we got it right, tested against a stop watch to fine tune for the track, a good Weber man could do it by listening to the engine and noting the response when the throttles were opened.

 

What I would like to know is how does the Lambada sensor know what the fueling is like at say 4000 rpm pulling out of a corner. ??

[welshpug 1,657]

you simulate the load and look at the gauge or datalog from the ecu.

Edited September 7, 2009 by welshpug

[wardy18 33 1 Cars]

I would prefer a proper wideband kit but for now a £14.99 lambda as Saveit has linked to on ebay looks the prefect solution, assuming as Boombang said that i can also get a boss kit for the exhaust

 

The next step then is to find out how i convert the multimeter readings to stoich readings??