Fuel Pumps

[Classik]

I've actually got all the bits in a box (pump, manifold gaskets etc) to replace mine - but I can still hear it whirring after a run so have left well alone. I just bought all the bits "in case"
I also kinda came to the view that making sure to run the engine lightly loaded for the last mile or 2, let it idle down a bit, and regular oil changes are the keys to longevity.

All wise comments & suggestions that are correctly respected here !

[Shoppinit]

Yeah, the last 2 or 3 miles in mine are at feather footed throttle. Even then I often have to leave it idling in the garage for a while until the oil temps drop back down to 90.

[Shoppinit]

Don’t know about the injectors I’m afraid. If you’re not getting lean conditions on WOT then maybe it’s not necessary. I don’t know what injectors bam is using on the mental manual. Presumably uprated ones to give 750+ bhp.

[Classik]

Don’t know about the injectors I’m afraid. If you’re not getting lean conditions on WOT then maybe it’s not necessary. I don’t know what injectors bam is using on the mental manual. Presumably uprated ones to give 750+ bhp.

Actually I do get lean conditions from time to time using e85 (not SP98). Maybe I should ask him in PM, thanks for the suggestion!

[Mɐʇʇ]

Only relevant if you know what duty cycle the injectors were running at at the time, otherwise it's just as likely a fuel pressure or mapping issue.

[Shoppinit]

I assumed he was mapped for E85.

[Mɐʇʇ]

Yeah, fair assumption.

But I caught myself out mapping an engine the other day - Lambda reported lean, so I increased fuel. Engine ran worse & still lean. So I increased fuel more, again.
Anyway, long story short, ended up rich enough that it was misfiring, meaning that lambda was reading excess oxygen, causing it to request to run even more rich and the whole system went unstable until it just demanded 8x midgets tipping large buckets of fuel straight in to the TBs.

So don't always trust what the Lambda is saying and make sure "everything else" is running just fine first.

[Classik]

Actually I have a small device which allows me to switch between 3 different maps: stock, optimized e98, and optimized e85; except for the stock one, those maps have been specifically tuned for my car and it takes like 5-10 min to upload a new map to the CPU, very convenient. Admittedly the e85 may have to be altered due to these (rare) lean conditions, but I guess the car would benefit anyway from a fuel system upgrade (fuel pumps + bigger injectors). FWIW injectors duty cycle have been measured at 85% on e85 at full load, and the car has registered 517HP on a dyno.

[Mɐʇʇ]

Sounds like size-wise, they're pretty well matched for what you need then?

[Shoppinit]

85% duty cycle is pretty high. I'd be worried that they won't be running linearly at that kind of load. Could explain your lean conditions at WOT.

[Classik]

Sounds like size-wise, they're pretty well matched for what you need then?

Well yes and no, as I have no margin for progress, and as Shopp just mentionned, 85% is already quite high, no?

[Mɐʇʇ]

That's interesting and I'll have to read up on it more. I've always understood that 85% was the sweet spot, so I'll need to research it some more.
But yeah, not much upside if you increase hp more, although imagine you could squeek a bit more on the fuel pressure if you really needed to?

Luckily this is just a hobby and I'm not a pro!

[Shoppinit]

And we're back to the original topic. After only 16 pages.

I wonder how much more pressure the OE pumps can provide sufficient flow for. Probably you wouldn't need much of a pressure increase because it sounds like your injectors are almost coping, or are coping and the issue is elsewhere.

I also wonder how the linearity of injectors changes with age / wear.

Can of bloody worms, innit.

[Classik]

Hahaha, yes that's exactly what I was thinking also: 16 pages to come back to the original topic, but well worth the journey!

I also believe the injectors are currently the weakest link in the chain so well worth investigating, and yes ageing doesn't help. Same apply to fuel pumps by the way. On the latter I've received some great feedback from local RS6 owners here and I intend to install an in-tank Walbro F274 (https://walbrofuelpumps.com/walbro-450l ... otive.html) and an in-line AEM 400lph (https://www.aemelectronics.com/products ... -fuel-pump).

[Shoppinit]

Cool. l'll be curious to see how you get on, especially with installing the pump in the tank. Take some photos please.