Which spark plug for E85

[FlyingScozzies]

Hi everyone.

I've been surfing the threads on this forum for 12 months or so, and it's been interesting reading. I think that I've learned a lot. Thanks particularly to Jardo, who's 'Must Do Modifications ,,,' thread was my map, and Prawn, who's build thread fuels the dream.

So, this is my first 'real' post, and I'm looking for help.
Car is an A3 with the AGU engine. It's got most of the mod's listed by Jardo's thread, but with a 'Mamba 9-11 GTX K04 Pro' hybrid turbo. The tune is a local (Sydney) tune by Ed at Quattro Sport, fueled by E85.

So, I was at a track day last weekend and replaced the plugs the day before with NGK BKR7E, in place of the Bosch FR7LDC plugs that had been there since before the turbo and tune were installed. I installed the BKR7E as I thought that they were a cooler plug, that would make a difference with the higher boost (21 psi peak).

Anyway, with no other changes except the plugs:

• The new NGK plugs suffered from a little miss-fire under load down low, but seemed to make a very linear power delivery through to red-line from around 3000 rpm. I was a bit ******-off at the miss-fire with the new plugs, even though the car was running faster than ever before. I was doing about 120 kmh at the top of a fairly steep hill on the track (sounds slow but it's a steep short hill that I could only manage 100 kmh up before). The car felt very drive-able with a 'fat' power delivery.
  
  
• Obviously the miss-fire down low would be slowing me down I thought, so I put the old Bosch plugs back in to see if the car was faster. The engine was very different with the old Bosch plugs in. The power delivery appeared later, with a definite ramp up in power from about 3500 rpm up to strong power at 4500 rpm going through to red-line. Much more 'peaky' and fun to drive. Funny thing was that I was still getting the same speed at the top of the hill so I'm guessing similar top end power. No miss-fire either.

My questions are:

• Can plugs make a real change to the way the 1.8t delivers power?
• Can the plug gaps be 'fine tuned' to make differences in power delivery?
• What plugs, and gaps, might be best using E85 fuel with the hybrid turbo? Does the lower burning temperature of the ethanol negate the usual need for a colder plug?

I'll talk to the tuner to see what he thinks, but I'm hoping that the Audi Sport experience may be able to shed some light on the issue.

Cheers in advance.

Iain

 

[<tuffty/>]

hey dude... you may struggle to get an 'Audi Sport experience' specifically on E85 as this is mostly a UK based forum and we don't have E85 on tap here...

I am sure we have a few of our foreign contingents that may be able to pitch in but don't be surprised if you don't get the answers you are looking for

What power are you at?, what gaps you currently using? are you sure the misfire is spark related not fuel related?

<tuffty/>

 

[FlyingScozzies]

Hi Tuffty. Thanks for your response.

I didn't think to ask if the rest of the world was using E85, or an ethanol based fuel. Sorry!
Still, maybe it would similar to methanol injection (but I guess that those systems aren't injecting 85% of the ethanol/methanol mix).

I haven't had the car on the dyno (rolling road) yet. My tuner's telling me 280 to 310 hp, but I'll see soon.

The gaps on the Bosch plugs were straight out of the box (twin electrode plugs}. These have worked well in the past and cured the miss-fire at the track.

The NGK BKR7E plugs were set to 28 thou' and missed slightly under load. I do understand that the miss could have been sorted by changing the gap on these plugs, but I had pretty much unlimited track time and was having way to much fun to stand in the pits trying to re-gap hot plugs!

Fuel wasn't the cause of the issue as the miss disappeared when I put the Bosch plugs back in.

Forgetting the E85 fuel then:

• Can plugs make a real change to the way the 1.8t delivers power, rather than just being good, ok, or rubbish?
• Can the plug gaps be 'fine tuned' to make differences in power delivery?

Thanks again.

Iain

 

[<tuffty/>]

Gaps will make a difference if you go too large... Typically set them to 0.7mm... This has worked on every 1.8t I have ever fitted plugs too...

7's should be fine at your power level and personally have only used NGK irridiums (although I did use coppers for a little while)... I currently use NGK 8's but I am at double your power on pump fuel..

Multi pronged plugs like Bosch super 4's etc don't seem to work too well in my experience ...

I am assuming your coil picks are OK...

BKR7EIX gapped to 0.7mm on fresh coil packs should not give you any issues

<tuffty/>