Author Topic: Mk5 gti on 95 ron fuel  (Read 1240 times)

Offline Pudding

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Re: Mk5 gti on 95 ron fuel
« Reply #15 on: July 17, 2020, 09:47:44 PM »
Bosch heat range is the opposite of the NGK.  The lower the number = hotter.  Grade 5 Bosch is equivalent to NGK grade 7. 
Thank you for this...I never knew this. I did find a heat range conversion chart and see quite a number of plugs differ in their heat ratings. I see Bosch is the only one with the larger number being the coolest...and the rest are opposite.

No probs.  I've never really liked Bosch plugs. The engines I've used them in have always felt slightly less energetic compared to NGK.  Can't really put my finger on it and it's not a night/day difference......but you can feel it none the less.  The only Bosch plug I liked was the old Audi RS2 plug, F5DP0R iirc.  That was a great plug in all manner of turboed VW engines  :happy2:
I know what you mean. The plug I like the most for my K04, because it has a feel that differs and never stumbles, is the NGK PFR7B.

Similarly, the NGK BKR7EIX with red top coils works really well in the UK climate and (very low) elevation  :happy2:  You guys in the Americas have a much wider range of temperatures and elevations to deal with.
« Last Edit: July 17, 2020, 09:49:30 PM by Pudding »


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Offline Ford 2

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Re: Mk5 gti on 95 ron fuel
« Reply #16 on: July 17, 2020, 09:49:41 PM »
I tell you what since changing to these plugs and the r8 coils I appear to get random misfires. Seems to happen in 20ish degree temps outside. I may have to look a bit deeper. It clears out and doesn't put on a light etc

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Offline Pudding

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Re: Mk5 gti on 95 ron fuel
« Reply #17 on: July 17, 2020, 09:52:08 PM »
How many miles on it?  Is it a hard misfire or just slight lumpiness on idle? The latter is quite common.

Injectors are another common source of misfires, usually starts on cylinder 3 for some reason.


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Re: Mk5 gti on 95 ron fuel
« Reply #18 on: July 17, 2020, 09:57:26 PM »
I have the slight lumpiness I live with that but twice now it has missed and popped/backfired through what felt like the intake under slight load. A good rev and it came right. Funny thing with the reds I find is they don't seem right in the head as if not seated correctly. I may investigate a bit. My car has near 140k I think. I've never done a fuel filter actually or anything to do with injectors etc.

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Offline ROH ECHT

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Re: Mk5 gti on 95 ron fuel
« Reply #19 on: July 17, 2020, 11:55:12 PM »
I can report when you are accelerating it at or near full throttle and it pops off a big backfire while losing all power...it may be fuel delivery. Mine did so when the fuel delivery was just 1.2 bar in the data at full throttle and starving for fuel due to failed LPFP/tank pump. Could also be the same result I suppose if a fuel filter was restricting fuel delivery.
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Re: Mk5 gti on 95 ron fuel
« Reply #20 on: July 18, 2020, 12:59:58 PM »
Mine was the opposite. under tiny load, quick rev and it cleared. It's not constant. Maybe twice in the last 3 months and I'm not sure but may have been low on fuel. Do people replace injectors or refurbished them ? Or are those fuel treatments any good ? Again thanks for the help

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Offline ROH ECHT

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Re: Mk5 gti on 95 ron fuel
« Reply #21 on: July 18, 2020, 03:16:03 PM »
Mine was the opposite. under tiny load, quick rev and it cleared. It's not constant. Maybe twice in the last 3 months and I'm not sure but may have been low on fuel. Do people replace injectors or refurbished them ? Or are those fuel treatments any good ? Again thanks for the help

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I just replaced mine not long ago. I didn't have them cleaned and pressure tested because they had 98k miles on them. If they weren't so old, I would have done that and it would cost $25 each injector for the pressure test and clean.

As far as fuel system treatments go...fuel is a pretty good cleaner in and of itself. Whatever the fuel isn't keeping clean, a bit of solvent diluted by gallons of fuel isn't going to help much in my opinion.

If possible, find VAG-COM and use VCDS to see the pressure data at full load throughout the rev range (2k to redline) for both low and high pressures...with MBs (230 and 231) showing both specified and actual. But if there is slight hesitation at lower revs, and on occasion only, then it could be a number of things such as: "spark plugs are old and worn out, air filter is possibly worn out and clogged with debris so its restricting the airflow. Intake valves are clogging intake air inlet. Oxygen sensor is a possibility. Or it could be a fuel filter/injector clogged/ fuel pump blocking proper fuel flow."
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Offline Pudding

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Re: Mk5 gti on 95 ron fuel
« Reply #22 on: July 18, 2020, 04:17:49 PM »
Injector 3 went on mine at 90ish K.  It was only noticeable at idle and very light loads as you described.  Under load and/or higher rpms, it was fine.  I replaced all 4 injectors because it's a pain in the arse getting the intake manifold off.  Didn't want to be going back in there again 10,000 miles later to do the other 3!

If you have a scan tool (VCDS isn the best) look for misfire fault codes.


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Offline GPem3:16

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Re: Mk5 gti on 95 ron fuel
« Reply #23 on: July 31, 2020, 12:48:53 PM »
Get your valves cleaned.
And injectors flushed/tested.

Well worth it

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Offline JR.303

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Re: Mk5 gti on 95 ron fuel
« Reply #24 on: July 31, 2020, 03:34:48 PM »
Thanks alot lads.. I'm going to change the plugs tommrow. I've took that cat out, put my decat in and it's going for a map next week. It feels much better but still not 100% hight up. I shall report back. Much appreciated
Have you done a pre cat delete? Mine was 219hp with it done standard (not ed 30) That was with 99 ron mind.

Offline Pudding

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Re: Mk5 gti on 95 ron fuel
« Reply #25 on: August 01, 2020, 12:52:44 PM »
That's a tidy gain for a delete.  I deleted mine (ED30) last year and it does seem a bit better up top but I never dynoed it. If it's anything like that much I'd be surprised/happy!  It also made the exhaust tone a bit bassier (factory system) which I like.


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