Jdm fuel pump upgrade

[dandan]

Hi everyone,

I know this is a recommended upgrade for almost any J spec car, nevermind a tuned one.My car (as far as I know) has the stock pump fitted.

While on the dyno (Pete Betts-Thor) we did a run at 1.3bar to check the fuelling. The car didn't go any leaner than 11.5afr, under boost when the 2nd turbo came online. Obviously, prior to this the fuel curve is a little "jumpy" during seq operation. This made 376bhp and 364lbft at the hubs.

My question is, does the pump definately need changing? I have stock 440's and no fse regulator (and don't want one). I am now pondering over the need for an upgrade to the pump as the afr suggests fuelling is ok. Is the usual reason for an upgrade because the fuelling leans off at these boost levels or is it one of pump life and longevity?

Also, what is the general consensus on bypassing/replacing the fuel pulsation dampener? Do you think this is something I should also consider?

Thanks in advance.

Dan

[alex h]

1. Don't know what age your car is but it wouldn't be a bad idea to replace it due to that reason alone...
2. Other than that it's not "necessary" but would be a good thing to especially noting the above and if you intend to get more power later.
3. The fuel dampener bypass is not really worth worrying about...would concentrate on saving your pennies for a proper fuel system if you ever use hybrids or a single/twin.
4. Your options for replacements are usually,
Walbro 341 - 255lph - can be used along side a second one for large HP requirements in the stock cage. Low voltage draw...tried and tested.
Stock UK pump - expensive but hard to better. Will supply ~600hp of fuel I believe.

[Nathan]

1. I would change the pump. You may well be supplying enough fuel but without a rail check you won;t know whether the pressure is dropping rapidly or not. One thing I will say- your pump will definately be flat out and personally I prefer not to see things sweat. Walbro is tried and tested and in our tests showed up to be superior to the stock UK pump (which is also more expensive).

2. I agree with Alex on the fuel bypass- you won't even be close to opening up the fuel lines etc. yet.

Incidentally- did you check power levels at both 1.2 bar and 1.3? You don't usually gain anything except EGTs...

[dandan]

see below, sorry

[dandan]

Alex, Nathan,

Thanks for the replies, much appreciated.

My car is a late 1996 for your information. I am not in any way against the idea of changing the pump I just thought I'd see what you'd say seen as the fuelling seems ok (afr wise). I appreciate the points about age and also rail pressure.

I won't go for the UK as I understand it daws more currnet than the jdm and also the Walbro. Is the Walbro a direct drop in or is there some fabrication involved? Also is it ok running on exactly the same elec wires as the stocker...ie ecu controlling 9v-12v changeover etc? Hopefully no need to wire in relays for constant 12v is there?

Is a pump change going to affect my afr, which at the moment is spot on. I do not want to end up running too rich as a result of a pump change.

As far as power outputs go (this is stock airbox and filter, fully decatted with restrictor ring in place, plus other mods too like bov, dsbc)

Obviously I can only give you a few no's and not an idea of the whole curve but suffice to say that although these are the peak figures, the gains are consistent across the whole rpm range:

1.05bar: 343bhp 5700rpm 326lbft 4500rpm
1.10bar: 355bhp 5700rpm 343lbft 4500rpm
1.20bar: 362bhp 5700rpm 350lbft 4700rpm
1.30bar: 376bhp 5750rpm 364lbft 4600rpm

The shape of the power curves at each boost level is almost identical and if anything the gains from 1.2 to 1.3 are the most prominent! I haven't driven the car on the road at 1.3bar at all since, I only wanted to check the fuelling as a precaution really.

Hope this gives you some idea... http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/smile.gif

ps When does the fpd become a restriction, what sort of horsepower levels?

Thanks all

Dan

[Nathan]

1. The Walbro draws less current than the UK but more than the Jap. The Walbro drops straight in, but yes you will need to wire 12v permanent with a relay as the walbro really doesn't like 9v.

2. Pump change should make no difference to AFR if you rail pressure was not dropping before. By the sound of it you can't confirm that so it may be possible that your afr's go out, yes. It's immaterial anyway- if you go rich after fitting walbro forget about the cost of re-mapping etc. just count your lucky stars you caught it soon enough..:-)

Should be fine though. I've never heard of a Mk4 being too rich on the stock fuelling with a Walbro but then there aren't many that are rich at 1.3 bar on the OE pump either so you got an oddball to start with...

3. Interesting figures on the power outputs...I'm surprised you gained at all but the added scare factor for an extra 14bhp.... I think you are wise to stick with 1.2. I guess you weren't monitoring EGT's either?

Not entirely sure when the fpd becomes a resriction tbh- I never had one on my big twin @ 1.4 bar but we've bypassed the fpd on anything more than that, mainly because we run dual lines and it's easier to just get rid of it. If you look close at one though you'll be amazed at how small the orifices are...

[dandan]

Cheers Nathan

You are right, I did not have an egt gauge fitted, it is one of my next mods (egt gauge, pump, fmic and small oil cooler).

Am i right in thinking that I wouldn't get those sort of gains from 1.2-1.3 if the egt's were indeed going too high? Just wondered, as I say it's a planned mod.

Glad you think the fpd is not a problem yet, more ? to invest elsewhere, like saving for the front mount.

AFR: Above 4500rpm my fuelling ranges from approx 10.8 at 1.05bar to 11.6 at 1.3bar. Once I fit the Walbro do you think it's likely my low boost afr (1.05-1.1bar) could drop into single figures? Surely this is not good for my power outputs not to mention piston rings?

[Nathan]

Yes, you can have power figures rising even though EGT's are rising as well. In fact, it's quite normal.

As for the AFR, you simply can't speculate. It doesn't get you anywhere. Fit the pump and re-check AFR's its the only way.

[dandan]

Thanks Nathan,

EGT gauge and Walbro will be added in the near future. No doubt I'll do it at the same time as my front mount and oil cooler so I'll be heading back to Thor anyway so the afr will be checked again.

Be nice to hit 390-400 at the hubs without upping the boost any more, but not sure whether to expect anything major (powerwise) from the fmic really but we'll see.

I will keep you posted.

[Martin F]

Quote[/b] (dandan @ Feb. 12 2004,20:29)]but not sure whether to expect anything major (powerwise) from the fmic really but we'll see.
That really depends on the state of your current intercooler.

If its seen better days you may make some significant gains. If its not too bad then as you suspect no major power hike.

[Nathan]

But at least you will manage to keep close to his 362bhp on a hot day. It's quite easy to lose 30bhp on the stock cooler, even more on a REAL hot day.

[dandan]

Thanks for your feedback guys.

My current sidemount is fairly shabby but I don't think it's tooo bad although CW did suggest a replacement sometime soon.

Hopefully I'll make some small outright gains, and as Nathan says, keep the figures high in the warmer weather too.

Regards

Dan