Tuning Mod

MikeT · Post by **MikeT** » 02 Jun 2010, 00:04

I must admit trialling the "resistor in the IAT mod" on the Ashtray (AKA Astra). I used a pot so I could "tune in" to the operative resistance range but the results were not as expected.

There was no evidence of excess fuel inasmuch the plugs remained an acceptable colour and the mpg didn't seem to change either.

I found it caused timing advance and with enough resistance, could induce pinking. Using my seat-of-the-pants dyno, there was no power improvement to speak of.

Maybe, on some cars, it might make a difference but I wouldn't let it anywhere near a petrol turbo engine.

citronut · Post by **citronut** » 02 Jun 2010, 07:51

Mike wrote
"on the Ashtray"

is this better than NICKARET? patch's, or can you just adjust the quantaty of fags you get through TEA HE

regards malcolm

handyman · Post by **handyman** » 02 Jun 2010, 11:05

Better fuel economy by increasing power?

GET YOUR HEAD DONE!!!!

H

Deanxm · Post by **Deanxm** » 02 Jun 2010, 17:42

By 'tuning' an engine in a sensable way you can increase both economy and power but you dont obviously get both at once if you have a heavy right foot. some H/C turbocharged engines for instance are capable of better cruising fuel consumption than their nasp sister engines.

D

citronut · Post by **citronut** » 02 Jun 2010, 19:38

i had the head portted/gas flowed on my old N/A BX 1,9D, what a diference it would happaly drive round town in 4th gear at 30mph, she would get up and go better than she did before, she used to go very well before,

also used only a sniff of fuel,

not realy any more top end though,

regards malcolm

Deanxm · Post by **Deanxm** » 02 Jun 2010, 20:43

yes a proper porting job makes a nice positve difference, the tct engine im working on now has huge fronds of metal 10mm long hanging down in the inlet ports from casting so it just goes to show how little effort goes into finnishing these parts.

D

steelcityuk · Post by **steelcityuk** » 03 Jun 2010, 11:20

Hi Dean,

The casting finishing on the TCT is terrible. That's why I spent so much time cleaning up the ports and the manifolds. The 2.1 head by comparison is very well finished.

Steve.

Stempy · Post by **Stempy** » 03 Jun 2010, 15:31

While the V6 has been in bits waiting for parts etc I have taken the opportunity to grind out and polish up as much of the terrible casting inside the inlet manifold as it's possible to reach. Don't know if it will make any difference mind, but I felt I needed to be doing something positive towards getting her back on the road.

Deanxm · Post by **Deanxm** » 03 Jun 2010, 17:53

Hi stempy

Dont polish the ports downstream of the injectors, just remove any large casting imperfections, the key thing to remember when porting is that you are not trying to increase air flow to the maximum you are trying to reach a perfect comromise between getting as much air as possible in whilst keepingthe airflow between the injector and cylinder turbulant enough to allow the fuel to mix properly, to do the job right you need a wet/dye flow bench to see how the liquid feul acts as it enters the cylinders.
The main point to concentrate on is the back of the valve head, valve seats (tri cut) and the shaping of the inlet below the valve guides, the valves spend very little time fully open so the ports arent the main limiting factor as far as air flow is concerned.
Have a look on the net, there is a lot to think about when porting, if you dont go into the job knowing what your trying to do you may well reducing power.

D

Deanxm · Post by **Deanxm** » 03 Jun 2010, 17:58

steelcityuk wrote:Hi Dean,

The casting finishing on the TCT is terrible. That's why I spent so much time cleaning up the ports and the manifolds. The 2.1 head by comparison is very well finished.

Steve.

Hi Steve

Yes my exhaust 'bar' was just the same as yours too, the N/A heads although being identical have a far better finnish though, im not 100% sure why the tct heads are so bad, maybe because being forced induction and aimed at torque rather than bhp citroen didnt feel it was worth wasting time with them???.

D

Stempy · Post by **Stempy** » 03 Jun 2010, 22:37

Deanxm wrote:Hi stempy

Dont polish the ports downstream of the injectors, just remove any large casting imperfections, the key thing to remember when porting is that you are not trying to increase air flow to the maximum you are trying to reach a perfect comromise between getting as much air as possible in whilst keepingthe airflow between the injector and cylinder turbulant enough to allow the fuel to mix properly, to do the job right you need a wet/dye flow bench to see how the liquid feul acts as it enters the cylinders.
The main point to concentrate on is the back of the valve head, valve seats (tri cut) and the shaping of the inlet below the valve guides, the valves spend very little time fully open so the ports aren't the main limiting factor as far as air flow is concerned.
Have a look on the net, there is a lot to think about when porting, if you dont go into the job knowing what your trying to do you may well reducing power.

D

I've not interfered with anything downstream of the injectors, only the big lump of aluminium that forms the bolt on inlet manifold on the V6. The casting internally was pretty rough with big lumps and protrusions and a very rough cast surface, so I just ground it down with a stone grinder wheel in an electric drill then smoothed it all off with a sanding wheel. The external finish of the manifold is far better than internal. Looking down the inlet ports of the cylinder head the finish looks a lot better and is pretty smooth.

Deanxm · Post by **Deanxm** » 03 Jun 2010, 22:53

can only be a positive difference it makes then

, your not tempted to get a rag on a stick with some metal polish and buff the inlets to a mirror shine then................i did on a bike i had...........never again

D

Stempy · Post by **Stempy** » 03 Jun 2010, 23:16

Deanxm wrote:can only be a positive difference it makes then , your not tempted to get a rag on a stick with some metal polish and buff the inlets to a mirror shine then................i did on a bike i had...........never again

D

I only polish the shiny bit's you can see which is why you can see your face in my rear brake calipers.

handyman · Post by **handyman** » 04 Jun 2010, 09:36

The trick to port 'polishing' is blending, ie, get rid of any obstructions in the inlet or exhaust so the flow is unimpeded on its way to and from the combustion chamber.

The ideal is smooth, with the surface down to a good 'flat' finish as left by a 200G flapwheel. It has been shown that a mirror polished surface can cause the atomised fuel to form droplets on the surface of the inlet port, which is wasted effort.

Increasing the size of the port, without understanding the conditions the engine will be working under can have a deterimental effect. Better effort is spent making sure all the components on the inlet or exhaust match, with no obstructions. Mismatched manifolds, gaskets that do not fit, bad castings are all worth checking and easy to rectify and give an easy power gain.

H

steelcityuk · Post by **steelcityuk** » 04 Jun 2010, 14:13

Hi Dean,

It could well be that was PSAs intention, if it's forced induction you can get the power in other ways. I've read in a XM book that PSA deliberately aimed for a high quality finish on the 2.1 manifolds but then again as no fuel flows through them and there's no throttling of the airflow it's a different matter hence the amount of time I'm spending on my 2.1. It seemed to work well with the 2.5 too.

Steve.