Is it worth porting a HDI head

[pugbug]

I've got a spare HDI head here, toying with the idea of getting it ported, never really complained about the lack of power from my HDI but, guess more is always better

Has anyone had experiences with doing this? I don't really want to a head change on a HDI and I'd rather have reliabilty any day of the week rather than a few extra ponies.

[Poodle]

The port shape on these is very important for swirl, if you port it and don't know exactly what you're doing you will lose that benefit, which will in turn see a loss of economy and efficiency. A friend looked into it once, enquired at a place that builds the HDi engine into tractor pulling beasties, iirc the bloke said he could get 10-12% without affecting swirl, not that much imo.

[Ruan]

Unless people know what they're doing when porting them, yes you can make them worse with ease, but there definitely are gains to be had.

I'd personally be sorting out the manifolds and turbocharger long before then, your money is better spent popping on a modern variable nozzle turbo and getting it working along with nozzles and a CR pump that allow for decent IQs at high RPM, you can add all the air you like up there, but if you've not the fuel, no point. I've seen very few motors that are actually capable of this!

[pugbug]

That settles that! I was just thinking of getting a mech engineer friend of mine to bore out the head and manifold to match. Instead I'm just going to get a meth kit!

[Poodle]

Are you coaling on boost? I'd be surprised if you need more air before more fuel, what turbo have you got at the moment?

[089]

I'd think the water/methanol kit will be used to lower EGR temps, not to add more air, no? even so, depending on power and how much boost is being made, it's doubtful how much gain you'll see (if any) from an H2O/Meth kit TBH except maybe improving a little on fuel burn consistency..

[shervo]

No, water/methanol kit will be used to lower intake temperature(lower intake temp = more dense) thus giving the effect of more air.

[pro_steve]

I found when playing around with Meth before (not the crystal kind) that even when I had really low intake temps of 20C (without an intercooler) and lots of boost, it still wasn't as good as an inter cooler. We came to the conclusion that the water must just evaporate and take up space that could otherwise be air.

Have you put a probe in to your intake to see what kind of inlet temperatures you're getting? Meths could be good but not too much in my opinion. I had them with an intercooler too, and on a dyno it added about 3 BHP across the whole range. Not really worth the money to me, depends what setup you have though.

[Ruan]

They're interesting findings, Steve!

Admittedly not a DI engine, but I found it made at real difference, as in you could actually feel it as it came on and the exhaust note totally changed - even with intercooling... If anything it made more of a difference on cooler days than warmer days, which I always found interesting!

What size nozzle were you using in your application!?

[pro_steve]

It was a long time ago, but as a guess it was 0.25 before the compressor and a 1 at the intake? Had the highest pressure pump too. Had a lot of methanol in there when I dynoed it.