Downpipe/Cat options

[shnazzle]

LTFT will be a lot more similar across banks than STFT. For LTFT the engine load and rpm becomes relevant. For cruising it will be on the lean side for efficiency, for WOT it'll be richer, etc etc. Different fueling for different circumstances. The tables are quite complicated and nobody on here knows (yet) exactly how they're calculated. So at what point did you take the measurements?

I'd say you're running lean if the LTFT across the range of load is always positive. I.e. The car is consistently having to increase fueling because it detects too much oxygen (lean) . But bear in mind that the MAF mod will artificially create this condition,doesnt it? I thought that was the point.

[CrazySX]

LTFT will be a lot more similar across banks than STFT. For LTFT the engine load and rpm becomes relevant. For cruising it will be on the lean side for efficiency, for WOT it'll be richer, etc etc. Different fueling for different circumstances. The tables are quite complicated and nobody on here knows (yet) exactly how they're calculated. So at what point did you take the measurements?

I'd say you're running lean if the LTFT across the range of load is always positive. I.e. The car is consistently having to increase fueling because it detects too much oxygen (lean) . But bear in mind that the MAF mod will artificially create this condition,doesnt it? I thought that was the point.

Are you talking about my LTFTs or Johns?  Mine are an average of my drive to work approx 40min varied drive on A/B roads.

Yes the MAF mod creates a lean condition, but then compensates with the bigger injectors.  

I have posted my fuel trims and mpg on Spyderchat and they all reckon something is wrong.  m http://www.spyderchat.com/forums/showth ... mod/page35 m

[CrazySX]

Little update. I sprayed some carb cleaner around the inlet side and no change in engine note so that's good news.

I tried to swap the sensors round and the bank 1 was not budging. Weird as I only had it out on the wknd  s:( s:(

It was spitting with rain so didn't want the car in pieces else no car to drive to work tomorrow lol so I left it and put everything back together.

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[lamcote]

Interesting, what do the Syderchat guys suggest it could be?

[CrazySX]

Interesting, what do the Syderchat guys suggest it could be?

something else lol! they reckon they are getting improved economy as a result of the MAF Mod.  I am monitoring MPG, this tank looks good, its currently done 140 miles and only down to just over half.  However... I find the top half moves very slowly and the bottom half very quick.

[lamcote]

I think comparing the consumption of first half of the tank v the second half of the tank is very confusing indeed:

According to info on this site the total tank capacity is 48 litres and the fuel light comes on with 10 litres left in it, that means you have 24 litres available in the first "half"  but only 14 litres in the second "half"  before the light comes on.

Not surprising there is a difference in perceived speed of usage?

[CrazySX]

I think comparing the consumption of first half of the tank v the second half of the tank is very confusing indeed:

According to info on this site the total tank capacity is 48 litres and the fuel light comes on with 10 litres left in it, that means you have 24 litres available in the first "half"  but only 14 litres in the second "half"  before the light comes on.

Not surprising there is a difference in perceived speed of usage?

Useful info once again bud! thanks for this, makes a lot of sense! its very reassuring to know there are 10 litres in reserve.  So technically i still have around 50 miles left at fill up (because i fill up when the light comes on or very shortly after).  This means i actually would get around 290 to a full tank which is VERY good and maybe 300+ if i drove like a gentleman :p

i am going to see at what miles i hit the light, then see if i can squeeze out another 30 miles, just for my own satisfaction  s;) s;)

[lamcote]

Isn't it safer just to fill up to the brim as soon as you can after the light comes on and then subtract the number of litres you can get in to the tank away from 48,  then you know exactly what your reserve is......

[shnazzle]

I don't consider it healthy running on the dregs of the fuel tank. But I guess with fuel filters etc these days the impact is minimal.

More importantly, it might be an idea to just return the car to stock, reset the ecu, give it good service (if it hasn't already recently) and then do some new readings as a baseline after driving around a few days (to set the LTFT etc).
Then you know what you're up against and maybe isolate an issue.

[lamcote]

Yep, I reckon that's great advice.

[shnazzle]

Yep, I reckon that's great advice.

That includes putting a proper air filter on  s:D s:D  
hahaha
Never going to stop harassing you about that mushroom in your bay

[CrazySX]

Isn't it safer just to fill up to the brim as soon as you can after the light comes on and then subtract the number of litres you can get in to the tank away from 48,  then you know exactly what your reserve is......

You're right. I just wanted to see a number higher than 240 on the trip meter lol.

I have been calculating as you have suggested, and the last one came in at 26mpg is that normal?

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[CrazySX]

I don't consider it healthy running on the dregs of the fuel tank. But I guess with fuel filters etc these days the impact is minimal.

More importantly, it might be an idea to just return the car to stock, reset the ecu, give it good service (if it hasn't already recently) and then do some new readings as a baseline after driving around a few days (to set the LTFT etc).
Then you know what you're up against and maybe isolate an issue.

This is what I should do, but I have priorities at the moment like getting the 200sx welded up before the work on the extension to the house begins  s:( s:(

Here are some snaps of my 200sx work just to give you an idea!








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[DanMr2Mk3SMT]

I cannot see your logic on the diagnosis?
I know, I need to block the tail pipes with a rag and check properly at the wknd. However wknd gone, I replaced a stud and nut on the 3 amigos and I cranked up some of the bolts on the manifold. So I know there are no leaks at the joints that would cause a rich ltft on bank 2 but.. the flexis are the only suspect thing before the sensor on bank 2 so my logic tells me it's got to be a leak at the flexis.

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There are three oxygen sensors in the exhaust system, two of which monitor the fueling:
Sensor 1 Bank 1
Sensor 1 Bank 2

These are the ones above / before the pre cats, so a leak in the downpipe is very unlikely to have any effect on their readings. The third sensor after the main cat is for catalyst efficiency and a leak would possibly cause a code there, but not a bank 2 rich code.

Can you hear any exhaust blow?

Hey can I check which flexi's were perishing,I have the Twin TTE exhaust as well was it the one that bends into the cat?

I'm having issues at the moment... Been told the blow in mine is from.thst but it's integral to the cat and they will only do a full replacement... At £2380...not going to fly

[Gaz mr-s]

You can buy flexi's on ebay & get a welder to replace them. 

[DanMr2Mk3SMT]

That was an option but just not sure of the parts, I couldn't get in when it was up on the ramp to take pictures

[Ardent]

Bit of work on here with tge search function will bring up those that have done it. Parts £70 springscto mind.

But maybe just a cats2you replacement and be done with it.

[Gaz mr-s]

I measured an old one 50 x 100mm.   You can get a pair on ebay for about £20

[Ardent]

At that price. My mention of £70 might include the welding.