A Little Help Please

[sutol 0]

No, it will run like on lower RON with stock timing or there will be a little difference depending on the rest of the engine spec.

 

I'm with Welshpug on this one, the more advance you can get in without pinking (using higher RON) the more power it will produce.

If not then throw the ECU away and put carbs on

[welshpug 1,622]

oh god Exile, please read this and let us get back on topic!!!

 

http://en.wikipedia.org/wiki/Octane_rating

 

right, Grez, your engine will run better on SUL (typically 97 or 98), particularly if the timing has been altered to suit.

 

what else did you want to know GREZ?

[Exile 0]

BUT, if you advance the timing to suit it will perform better

 

I suppose You've read it, but didn't understand at all.

 

I thought it was part of this topic -prove me i'm wrong. Also, this topic is a fortune-telling story. We don't even know what kind of engine do GREZ have. Probably every possible cause was already mentioned, and now it's GREZ turn.

Edited August 12, 2007 by Exile

[Guest Grez]

My engine is a 93 1.9Gti which unfortunatly has a cat. Well i drove it today and its become worse, it sounds like the cats rattlin and it smoked alot from under the bonnet. Also the pick up is like waiting for xmas a 1.2 did me . Anyway figured the smoking could be oil coming from the dipstick and dripping on the exhaust and also the Distributor. Im not even sure if its running on all cylinders either anymore. Ive tried to use 98 ron but it means driving miles to fill so its using 95. Im going to go try 98. Just more problems have happened. The timing could use a tweek so could the ignition. The passenger windows packed in too but thats easy . Any more pointers advice and help are welcome. As im pretty p**sed my mechanic said it was in good shape and by driving and feelin its easy to tell, im trying my best to keep this beauty on the road.

Edited August 13, 2007 by Grez

[Jrod 7]

I seriously doubt any amount of ron will fix that, sounds like something has deffo broken.

[stux 0]

I seriously doubt any amount of ron will fix that, sounds like something has deffo broken.

 

Absolutely agree!

 

It is also very hard not to agree what Exile said:

 

For me it looks like your camshaft is ending, or there is lack of fuel (pump?) If you have jetronic it might be AFM or engine temp sensor.

There is still an option with wrongly fitted timing belt.

 

To say a word in discussion about fuel octane ratting.

 

Generally fuel characterised by higher RON number burns less rapidly and is resistant to detonation at high compression and temperature.

 

That is why A. Graham Bell in “Modern engine tuning” says:

“… a high octane fuel will not increase power unless the engine actually needs a fuel which is chemically stable at high temperature and pressure. Obviously, if the engine does not have a compression ratio and spark advance great enough to produce high combustion pressure and temperature, then the high octane fuel will not burn completely during the early phase of the power stroke, resulting in loss power.”

 

Unless the engine pings, lower octane fuel will be better!

Edited August 13, 2007 by stux

[jackherer 543]

That is why A. Graham Bell in "Modern engine tuning" says:

" a high octane fuel will not increase power unless the engine actually needs a fuel which is chemically stable at high temperature and pressure. Obviously, if the engine does not have a compression ratio and spark advance great enough to produce high combustion pressure and temperature, then the high octane fuel will not burn completely during the early phase of the power stroke, resulting in loss power."

 

Your XU9JAZ engines don't have adjustable ignition advance, our XU9JA engines do. If we retard our ignition spark timing so the engines do not ping on 95 RON fuel this results in performance and economy becoming VERY BAD.

 

You can read books as much as you like, but until you try different fuels in a car with adjustable ignition timing you simply don't have any practical experience of this issue.

[GLPoomobile 958]

Guys, I'm sorry to jump on the bandwagon and continue the slightly off topic skew that this has taken, but I've just read the topic for the first time and can't believe some of the s*ite

 

 

If You say so... I'll stick to my experience and little knowledge

 

This quote sums it up in a nutshell. Exile, you are arguing the toss because YOUR car and YOUR experience differs to that of many experienced members on this forum. Members who have a long track record with GTIs. Let alone the findings of people driving similar cars, and what has been reported in some magazines.

 

I for one have personally never noticed a dramatic difference in 'speed' when using 97 or higher RON, with advanced timing. BUT I have noticed better economy. In all honesty, the fact that I have not noticed a difference in speed - good or bad - is more likely down to the fact that I'm not very good at detecting minor differences whilst driving. That's a personal thing. But I wouldn't be so stubborn to suggest that everyone on here who claims to the contrary is wrong just because it doesn't fit with my findings

 

Anyone can pick up a book and recite someone else's professional opinion (I'm the first to admit that I'm guilty of recycling knowledge on this forum that is not 1st hand experience, but rather stuff I have read and trust to be correct and I have committed it to memory), but sometimes you have to accept that the greater public opinion, based on actual experience, is equally as valid.

 

Nobody on here is trying to suggest (I hope) the Max Power (et all) myth that any car can gain 20bhp by using 101 RON race fuel. But the simple fact is that these engines are designed to run at their optimum on 97/98 RON, and just because they can be made to run on 95 doesn't mean that they perform as well as, or better on it. And I wouldn't question the validity of this considering the shear volume of Pug enthusiasts over may years who have confirmed this through experience. If your car responds better to 95 for some bizarre reason, then use 95, but don't suggest that everyone else is wrong. Maybe the higher RON fuel you have used has just been poor quality

 

End of rant

[Exile 0]

This quote sums it up in a nutshell. Exile, you are arguing the toss because YOUR car and YOUR experience differs to that of many experienced members on this forum. Members who have a long track record with GTIs. Let alone the findings of people driving similar cars, and what has been reported in some magazines.

GREZ have 120hp motronic like me, not a 128 JA like You, and it runs best on 95. Do You actually need 'long track record' to know which fuel suits best? Someone who drives GTi for about 10 years will have wider knoledge, than someone hwo is driving 5 years? Not necessarily.

BUT I have noticed better economy

without lambda or knock sensor? Impossible. You always have same AFR (inlet) Engine isn't intelligent and don't know how the fuel burns. Injectors are to inject the same amount of fuel. Doesn't matter if it's 95,98 or frites-oil from mc donald's. The only gain is better performance on same throttle (which should improve economic), but if there is no better performance...

 

If there is so many magazine articles and a lot of member tested it -prove it and show me some dyno results (not from BP or sth)

[stux 0]

I don’t believe that anyone can feel the difference between 95 or 98 RON by driving only if engine doesn’t ping on 95 fuel! It is hard to measure differences (power or acceleration) even on a dyno because of measurement accuracy.

 

Fuel quality is much more important than RON no.

 

Fuel should be adequate to compression and ignition timing!

[jackherer 543]

GREZ have 120hp motronic like me, not a 128 JA like You, and it runs best on 95. Do You actually need 'long track record' to know which fuel suits best? Someone who drives GTi for about 10 years will have wider knoledge, than someone hwo is driving 5 years? Not necessarily.

without lambda or knock sensor? Impossible. You always have same AFR (inlet) Engine isn't intelligent and don't know how the fuel burns. Injectors are to inject the same amount of fuel. Doesn't matter if it's 95,98 or frites-oil from mc donald's. The only gain is better performance on same throttle (which should improve economic), but if there is no better performance...

 

If there is so many magazine articles and a lot of member tested it -prove it and show me some dyno results (not from BP or sth)

 

Your XU9JAZ ignition timing is controlled by the ECU and fixed. It is mapped for 95 ron so it will run exactly the same on 95, 97, 98, 99, 100 whatever.

 

Our XU9JA ignition timing is controlled by a mechanical distributor that can be advanced and retarded manually. Therefore it is possible that GLPoomobile acheives different fuel economy with the same fuel management as the IGNITION TIMING IS DIFFERENT.

 

 

(I'm using bold and caps now so I hope you read it if not I'll try increasing font size next time as well )

[Exile 0]

Maybe You've missed it:

 

From wiki linked by welshpug (who also told as about advancing)

 

Octane rating has no direct impact on the deflagration (burn) of the air/fuel mixture in the combustion chamber. Other properties of gasoline and engine design account for the manner at which deflagration takes place. In other words, the flame speed of a normally ignited mixture is not directly connected to octane rating. Deflagration is the type of combustion that constitues the normal burn. Detonation is a different type of combustion and this is to be avoided in spark ignited gasoline engines. Octane rating is a measure of detonation resistance, not deflagration characteristics.

 

You are all telling me something which You can't prove by anything, but Your opinion.

 

PS: dark -shell V-power racing 99

light -normal 98

http://www.chojnacki.com.pl/wykresy/32.jpg

[stux 0]

These are the results for Fiat Panda 1.2 (CR 9,8:1). This part of article comes from one of the best and the oldest Polish automotive magazine “MOTOR”

 

 

- fig.1,2 – acceleration on 4th and 5th gear

- fig. 3 - max. bhp (measurement accuracy +/- 1.5 hp)

 

With this CR there are no measurable differences so if someone want to pay more for “better” fuel …

Edited August 13, 2007 by stux

[GLPoomobile 958]

GREZ have 120hp motronic like me, not a 128 JA like You, and it runs best on 95. Do You actually need 'long track record' to know which fuel suits best? Someone who drives GTi for about 10 years will have wider knoledge, than someone hwo is driving 5 years? Not necessarily.

without lambda or knock sensor? Impossible. You always have same AFR (inlet) Engine isn't intelligent and don't know how the fuel burns. Injectors are to inject the same amount of fuel. Doesn't matter if it's 95,98 or frites-oil from mc donald's. The only gain is better performance on same throttle (which should improve economic), but if there is no better performance...

 

If there is so many magazine articles and a lot of member tested it -prove it and show me some dyno results (not from BP or sth)

 

I don't have a 128JA thanks very much.

 

You can sit at your keyboard till the cows come home and accuse me and everyone else of making this stuff up, but I know that my fuel economy is better when running 97/98/99 RON fuel. I've had 2 x 1.6 8v, 1 x 1.9 8V and now have a 1.9 Mi16 (not driven enough yet to know how it reacts to different fuels) over 7 or 8 years. 99% of my driving over the years has been daily commuting - same route, same conditions, same driving style day in and day out - so I do get a feel for what my economy is like. And I am sad enough to actually calculate it properly on a regular basis. So quite frankly I don't give a hoot if my experience contradicts the theory, I'm going to stick with pure tangible fact from my own experience.

 

My comments about people who have driven Pugs for years was not meant in a patronising way either. My point was that if someone has driven a multitude of 205 GTIs and has racked up considerable mileage in them, and has by and large noticed an improvement in performance and/or economy, then I'd say that their experience counts for more than what a book suggest the truth SHOULD be.

 

Let us also bare in mind that just because we may share the same engine, it does not mean that what is best for one engine is best for another. They are old cars now and will all vary greatly. For example, just because Someone with an identical spec Mi16 to me says I should go and fill up with BP Ultimate as it is by far the best fuel in their experience, does not mean that I'm going to find the excatly same result. I may find that Shell V Power works better for me.

 

And finally, I am not about to try and dig up a load of articles to satisfy you and vindicate me. I read a lot of magazines and spend a lot of time on the internet. I don't believe everything I read, I'm old enough now to be able to filter at least 85% of the s*it that gets waved around as the truth (I hope), but the point is that I HAVE read legitimate articles, and have heard opinions of other car owners on other forums that substantiates what most of us have said on this forum. But I'm not going to trawl the net in an effort to rake up some of what I have read in the last x years just because you want me to justify my comments.

Edited August 13, 2007 by GLPoomobile

[jim21070 2]

Your XU9JAZ ignition timing is controlled by the ECU and fixed. It is mapped for 95 ron so it will run exactly the same on 95, 97, 98, 99, 100 whatever.

 

Our XU9JA ignition timing is controlled by a mechanical distributor that can be advanced and retarded manually. Therefore it is possible that GLPoomobile acheives different fuel economy with the same fuel management as the IGNITION TIMING IS DIFFERENT.

 

Absolutely!

 

Right Grez, to help a little more with your issues. Knowing you have an XU9JAZ puts a slightly different complexion on things.

 

If it is not running on all four cylinders it will both be very down on power and very rough running. To discover why, you will need to do some tests. I'd start with a compression test, then check cam timing. Both are easy and the former will give a good indication of the condition of the pistons, bores and valves, especially if you do a "Wet and Dry" compression test. I'll explain more fully what that is if you need. You also need to check that you have sparks at all four cylinders. A quick "read" of the spark plugs will help identify if you have a cylinder or cylinders running a little below par. They should all look much the same, a light tan colour.

 

You rattly cat may well be a contributor as the cat may be partially blocking the exhaust. This will have a significant effect on power. Also, as you have Motronic management, do you have the "K" engine Management light on? I'm wondering if your Lambda sensor may have failed and is causing poor fuelling. It may be a good investment to have a local garage pop a gas analyser on the exhaust to see if the injection is fundamentally behaving itself.

 

Take it step-by-step and the solution will be found.

 

You may wish to open a new thread in the XU Engine amd Gearbox area of the forum to continue this

[jackherer 543]

You are all telling me something which You can't prove by anything, but Your opinion.

 

Read a proper textbook, I recommend Introduction to Internal Combustion Engines by Richard Stone, I have a copy right here and I was about to type a big section in but I really can't be bothered.

[Exile 0]

Stux already have put a G.Bell text and what? Of course we are all wrong, and dyno results from me are fabricated to.

 

PS -It can't be faulty lambda sensor.

[GLPoomobile 958]

Sorry to the original topic poster for this continued hijack I wish to continue the debate as I find it quite interesting. Maybe a Mod would like to move this to a seperate topic>

 

There's 2 seperate arguments going on here (including the original problem that poster is having) - 1 is that of what fuel is best to use in a Cat equipped 1.9 with Motronic (sorry I can't remember engine codes), and the other is the validity of whether performance and economy CAN be improved on a earlier 1.9 with Jetronic and a dizzy.

 

Fuel should be adequate to compression and ignition timing!

 

Exactly. The 1.9 dizzy equipped GTI was designed for 97 RON fuel. Running it on 95 results in pinking in most cases and therefore the timing must be retarded. This means the engine can run without pinking, but performance is sapped (and performance and economy are linked to some extent as far as I am aware). Conversely, if you wish to improve performace slightly, you can apply more advance to the timing, but eventually you will reach the point where the engine begins to pink again, and if you wish to advance any further then you are going to need to use higher RON fuel again. Hence why we have continued to argue the point that by using higher octane fuel and adjusting the timing to suit, many of us have experienced better performance and or better economy.

 

If my logic or knowledge is completely wrong on this then correct me. I haven't studied books and I'm not a trained engineer etc, so forgive my ignorance.

 

Your XU9JAZ ignition timing is controlled by the ECU and fixed. It is mapped for 95 ron so it will run exactly the same on 95, 97, 98, 99, 100 whatever.

 

If this is the case (I don't know anything about Motronic or the later 1.9 engine), then I can understand the logic that a higher octane fuel will have no benefit at all, or possibly be worse, if the engine cannot advance the timing to take advantage. This contradicts what an earlier poster said about running this engine on higher octane fuel. I suppose that if the engine is not advancing the ignition to compensate for the higher octane, and higher octane burns slower, then may be it is feasible that it will not perform as well.

[Jrod 7]

[sutol 0]

 

 

[Exile 0]

The 1.9 dizzy equipped GTI was designed for 97 RON fuel. Running it on 95 results in pinking in most cases and therefore the timing must be retarded. This means the engine can run without pinking, but performance is sapped

I don't argue with that -You are correct. But sometimes on good fuel, even a JA runs better on 95 (fuel MUST be good)

If this is the case (I don't know anything about Motronic or the later 1.9 engine), then I can understand the logic that a higher octane fuel will have no benefit at all, or possibly be worse

This is correct too. Unfortunately using higher octane number, than the engine is designed for and advancing timing won't (stock engine witch stock compression) give us more performance. It's just a placebo effect.

Edited August 13, 2007 by Exile

[jackherer 543]

But sometimes on good fuel, even a JA runs better on 95 (fuel MUST be good)

 

thats simply not true, if you've experienced that then the petrol station must have mixed their tanks up and actually given you 97.

 

Unfortunately using higher octane number, than the engine is designed for and advancing timing won't (stock engine witch stock compression) give us more performance. It's just a placebo effect.

 

I accept that due to the lower compression ratio the JAZ will not develop any more power on 97/98 even with more ign. advance BUT equally it will not be worse.

[Baz 421]

Right, just to throw some more 'fuel' on the fire.. ( sorry!! )

 

From what i understand and to kind of align with what's been said here by GLP, Jackherer etc, the 'RON' number tells nothing about the actual power or economy of a fuel, it's the measurement at which the fuel is resistant to knock. So yes IF, and only if you can adjust the engine's parameters (Timing) to accept the fuels higher anti-knock ability then both economy and power can be had.

 

Not sure whether that may help anyone else understand it as it does me!

 

Just to add, if you're after a performance fuel, pay more attention to the MON rating.

 

Hmm, this has gone way O/T!!

 

Edit; sorry just realised basically the same as what i've said has already been said a few times in previous pages..

Edited August 13, 2007 by BazGTMi