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EJ20 E85 spark plug heat range

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Hi all,

currently working on multiple EJ's on E85 , all these cars have a really rough cold start with several missing cilinders untill they get some heat in them.

there's not much ecu-wise i can do as these Autronic ecu's are very basic on coldstart and only have 1 general warmup table.

so the question : are 8-9-10 NGK heatrange sparkplugs really necessary ? i think the use of these plugs is a leftover from years back when they all where still racing on pump fuel. they all have an intake restrictor so the engine is really struggling up high in the rpm range in top gear

I think you may be mis-understanding the whole point of different heat ranges for the spark plugs.

The heat ranges are to keep the spark plug centre electrodes in the range between being two cold which can allow deposits to build up and being too hot which can cause pre-ignition and even melting of the electrode. In the old days, it wasn't uncommon to have 'hot' 'plugs for starting and warming up the engine, which would be swapped for 'cold' plugs for the race.

Modern spark plugs have a much wider operating range, but the still need to be carefully selected to match the operating conditions the engine will be used under - generally, the more power the engine is producing, the greater the heat and so requirement for colder running spark plugs. That you may be having some cold starting problems really shouldn't be taken into consideration as that won't destroy your engine.

That said, I would expect there to be one or two things causing problems - ethanol doesn't atomise well at low temperatures and it's worsened with large injectors, which can make it difficult to get a good mix and burn, it's also common practice to run very narrow 'plug gaps which will also have issues igniting the mixture. Correctly sizing the injectors and where possible using designs that enhance atomisation will help, as will upgrading the ignition to give reliable ignition with wider plug gaps.

i asked the question because i didnt dyno these cars myself so i cant check them after wot and i have no interpretation about them behaving in full boost

they still missfire when the engine is warm and you drive around in cruise area's

Most cars i tuned myself where on NGK 7's for 100 hp more on regular pump fuel so running 8's or even 9/10 looked a bit overkill for me

Ah, I'd expect one, maybe two heat ranges for a moderate power increase, especially if running at peak for extended periods.

The main problem with going too cold is fouling of the spark plugs, which can lead to misfires.

As it is, unless you have a chance to do a proper check, it's going to come down to guesswork what's causing the misfire - it may be a messed up tune.

I'm completely rewiring one car from the fleet and putting a Link in which i'll tune myself , so we'll see how that works out

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