Fuel Pump, Decat + Remap = Lost 30bhp and running lean
 

Hi all, had a decat downpipe fitted a few weeks ago and car was road mapped by a reputable OS mapper. After the map I was told that the car was breathing better as expected, so fuelling was upped to match - hence I should expect more power. Yay!

My car (2005 STI) made 315 BHP on the Scoobyclinic rollers back in December, and today I had it on the rollers at RS Tuning in Leeds which showed me ay 284.6bhp and the car running "very lean for a Subaru" in words of the Dyno technician.

The first two graphs below are from December, with the final three being from today:
https://lh6.googleusercontent.com/-8...832-no/002.jpg

https://lh6.googleusercontent.com/-v...-no/SC+001.jpg

TODAY:

https://lh6.googleusercontent.com/-e...-no/RS+003.jpg

https://lh4.googleusercontent.com/-8...-no/RS+002.jpg

https://lh3.googleusercontent.com/-B...-no/RS+001.jpg

In addition to the lower power and AFR, the peak boost seems to be slower now than it used to be. I'd expect the opposite after going decat :confused:

I've opened up dialogue with my mapper and I've sent a copy of the graphs over for him to look over. He's a great mapper with a great reputation, so I'm sure it's more likely something which has changed on my car in terms of hardware since he did the map.

Any ideas?

Which fuel pump did you buy?

There are various Walbro pumps on the market and some have quite bad reputations. I believe the SWRD has also had issues.

Its an SWRD one actually. If I source a walboro one, would my map need tweaking for it?

I'd contact the supplier first.

There was a gb running on here and one of the buyers maxed out at about 300bhp and was told by the mapper that it was down to the fuel pump.

Quite often engines are mapped lean when the mapper can here det, usually on piston 4 to save the engine.

Did the mapper give you any idea what was holding it back?

Might be worth giving the clinic a call as they see this a lot and mainly as you're car has been there before. They do state the main problem is us, the customer. We tend to go to one place for one thing, and the next for another etc. The customer then goes to the clinic who has to start all over.

I personally chose an RCM pump. Cheapest place is on ebay through advanced automotives. The reason; never heard anyone complain about them and of course RCMs rep.

The mapper gave no indication it would be lean and/or down on power when he mapped it. He actually said to expect 10-15bhp improvement over my 315bhp base.

That suggests to me something may have failed or be struggling since the map?

It could be all sorts of things. Was the car mapped on the road or RR?

It could be that the clinic just did a better job.

Hopefully someone with a lot more knowledge and experience than i will be along soon and be able to diagnose better by looking at your graphs.

Just confirm, UK or JDM and all mods and what ecu as well. Might also be worth cutting and pasting thread into the ECU section. GL

Just to clarify, SC never mapped this car it simply went on their dyno during an RR day.

The same mapper did the mapping before and after the decat.

Car is UK spec, 255lph swrd pump with scoobyworld 2.5 decat turbo back, prodrive backbox and k&n panel filter.

Hi there

Every dyno is different and back to back test,will be best to do on same dyno as previously

If running lean,there can be leak or as above fuel pump,with fuel pump,we running HRC which has been spotless

Jura

Surely you'd over fuel to stop det? Running lean is worse than over fueling.

Thanks guys, Jura I'm prepared for inconsistent results between different dyno setups in terms of bhp but I expect boost and afr to be more consistently measurable?

30bhp is a lot to put down to the dyno I fear :(

Hi there

30bhp between the dyno difference,not sure if lot,but hopefully Shaun or any mappers can confirm,can be this cause

Lot depends on conditions and mostly too on operator of the RR.

Boost be too consistent,but above this can depend on conditions,AFR should be too consistent,but as above I would try different dyno

You are used same fuel(V-Power or T99)

Jura

i wouldnt worry, mine did 320bhp at one dyno after remap, and then did 287 at rs tuning with the same worry too rich or too lean, cant remember which he said, got mapper to check it over after the map at the time, all spot on. everybody seemed to get low figures on the day other thean the standard cars , which didnt make sense, somethings not right with that dyno

Did you tell rs tuning who mapped car? As they don't like some mappers and will spout some to mock the map!
Does the car feel good as terms of drivability? I wouldn't worry as like others have said dynos vary considerably either very low or surprisingly high on a turbo that hasn't seen a figure that produced, best way to check is go back to sc rr for a better confirmation.

I've now heard a few RSTuning horror stories from a couple of forums :(

What makes things worse (or better?) is that en route to the RR day today, I said to my passenger "I'm convinced it's down on power".

When I collected the car a few weeks ago after remap, it felt like the fastest car on the road - but then I'd spent a few days driving a 1.2 Corsa so my arse-dyno was out of calibration a bit. As the last couple of weeks went on, I felt the car was a little lethargic but I excused it on warmer weather and the fact I was "getting used to it".

Todays RR results sort of made me feel a bit better, as the car would indeed appear to be slower - but the RST horror stories I'm hearing are making me reluctant to spend the time/cash going to somewhere like SC. Even if I go to SC and confirm there is a problem, I would then need to spend the bucks to get an Ecutek license as my current map is OS :(

Busta, I think they knew who mapped it because of a comment that was made (not slagging anyone off, just a passing comment because another car present had been mapped by the same person) - but I can't remember if that comment was made before or after it was mapped.

why guess what the problem is....? go see a reputable tuner and get the AF tested, or call the mapper and book in.

Many little things can wear out, go bad to change the cars feel..... including weather and heat.. often forgotten.

guessing is for fools!

They'd be able to tell anyway once on the equipment.

Just read that when it was mapped it was good but then later when you drove it it felt underpowered then my suggestion is talk to your mapper, something might have worn/gone/broke etc as the car is seeing more strain it could be something's come loose etc

The shape of the graph and the lean trace would point to it pulling timing presumably because it is lean. However it is difficult to be sure with regards to power gain when its run on a different dyno before and after.

Why?

The afr is a measurement the same as the power is, if your expecting bhp to be inconsistent what makes you think boost and afr will be?

Spool point also is effected by the gearing settings btw

Thanks for the insight JGM.

My "expect boost and afr to be more consistently measurable" is only a perception I've got. My perception is based on the fact that boost pressure is easy to measure, as is engine RPM. You've explained that by the gearing settings though, so may be a dyno operator error(?)

I see the AFR as being basic chemistry, but I guess faulty equipment or poorly calibrated equipment can misread it - but the fact is, all three pieces of data all point towards something being amiss with the car rather than three independent components of the dyno, is that a fair assumption?

I did a quick Google to see what "pulling the timing" means, is it as scary as it sounds - and should I avoid doing any mileage in the car until I get this properly diagnosed?

I'm not going to guess through this problem, I'll get my mapper and a reputable tuner involved on Monday - but I feel posing questions on forums can always help, even if I just learn a few things along the way.

Thanks again all, I'm not shy of sending my car off to a specialist - but any further info or suggestions is always welcome to give me something to ponder over the weekend.

Afr sensors wear and usually each dyno has a uniquely altered fitting that get shoved up the tail pipe. In theory they should match or be similar but so should power and torque but in reality they often arent.

The boost sensor has a reset to 0 function but if its a high pressure or low pressure day it will effect it. They arent often reset in my experiance.
The spool as said already is effected by gearing entered or whether measuring engine rpm with ht lead clamp or from roller speed. This also effects the torque but not the power reading.

Cheers JGM, learning all the time :)

I've got an ODBII adaptor and app for my phone, was playing tonight and it seems to have an AFR measurement. Is this going to be accurate at all and worth paying attention to?

From what I can gather I should be expecting an AFR in the region between 11.0 and 12.0 at WOT, with it being higher (leaner) at idle.

I've just been researching a few reasons for running lean, stuff like post-MAF leaks worth checking out?

It also seems like most people get a CEL thrown up when running particularly lean - and my codes are clear.

Just to stress again, I'm not substituting a proper visit to a proper specialist - I just would like to gather if possible whether a) the lean readings from today's Dyno are even correct and b) if it's serious enough to consider parking the car up until I get it looked at.

It's a daily driver but I can do without if it needed, I just need to make arrangements y'see :)

The only way to check the AFR's is with a wideband, your app and the factory O2 sensor won't help you.

Cheers bluenose, I'll not waste any time with that one then :)

Just a wee update, I'm meeting my mapper on thursday to check things over. His comments mirror that of JGM with regards to the ECU pulling the timing but he's not ruling out the dyno conditions as a cause. (heatsoak etc).

I'll update on Thursday, hopefully she's healthy and it was just the circumstances of the dyno run.

I would echo what simon says and have seen afrs vary by the order of one whole afr point dyno to dyno as depending on the condition, make and location of the sensor it has a huge impact as does the home made nature of most afr probes.

does look like there is an issue with timing being taken out though but dyno and fan set up can have a huge impact on that.

it is all too easy for a dyno operator to make a car look bad and play on pier pressure/fears on dyno days to drum up mapping or other work for them.

i hope your mapper gets to the bottom of it :thumb:

Thanks mate, appreciate it.

Your words echo pretty much that of everyone I've been speaking to in the mapping business, or even just people with knowledge of these cars :)

I'll know either way on thursday with any luck, then will book in on a different dyno just to draw a line under the whole thing!

Def +1 :thumb:

I was hesitant to name my mapper because I know how violent internet forums get when names are matched with a concern... but I went to see Andrew Carr today.

He spent an hour or so with me, first checking some kind of "correction table" which he explained as being a measure of the compensations which the ECU has made since the map. Knock correction was at zero and AFR correction was very close to being zero, nothing out of the ordinary.

We did some WOT runs in 3rd and 4th whilst he logged and he said everything was spot on, AFR worked out to be around 11.4 which is how it was on the Scoobyclinic Dyno back in December.

I've got no idea what could have happened on the RSTuning Dyno, but everything we did today suggested the car was running fit as a fiddle.

Andrew has suggested if I want a power run on a Dyno, to coordinate with himself and he can log the session so IF we get another odd result - he'll be on hand to diagnose on the spot so I may take him up on that offer.

On top of all that, Andrew didn't charge me a penny for effectively wasting an hour of his time - top bloke :)

I've been driving the car off boost since the dyno run, but on the way home today I gave it some beans and it felt quick as ever - so I guess my "it feels slow" prior to the dyno event was purely getting used to how it pulls... but who knows!

Thanks for all the help, even if it's come to nothing.

:thumb:

Now you need to take it to sc dyno to compare, wait for a dyno day at sc, I'm sure ukscoobies have em from time to time.