[bocean02]

I just got myself a new 900S project, I have always wanted one of these so am well chuffed! However, the fuel economy at present is shocking at around 20mpg which is far more petrol usage than imagined. I found a leak at the fuel filter which appeared to be the problem so I replaced it but if anything now, it's worse! I replaced the vacuum hose a while back but didn't replace it with a standard part but instead with what I thought would 'do the job', would this have an effect on the fuel economy? I had an emmisions test the other day, all good in fact very low. I have serviced it all within the last two weeks and nothing has changed. Please can someone advise my next move, thanks.

While i'm here, is there a huge difference between the high pressure and low pressure turbo's? Can I switch without to much arsing around or there a different cooler system etc.?

 

[Horns]

Difference between the two is about 30 bhp and a fair whack of torque. You need to fit an intercooler from an ftp and then one of two options to increase boost. The tricky way is to transplant the APC system with its associated loom and sensors. The simple way is to fit an MBC (basically an inexpensive valve) instead.

I went for option two - its simpler but you have no knock protecton. I'm running 1.1 bar of boost (stock is about 0.7, LPT about 0.4 I think) with no issues so far. Plenty others have done the same. Its a cheap upgrade that makes a big difference to performance.

EDIT forgot to add, my LPT when stock got about 28-30 mpg.

 

[ShadowWorks]

I have some how gotten 30Mpg in summer and now that its cold I get around 20Mpg and I have my fuel system running lean, these cars are not good on fuel not even the N/A are good on fuel, its a shame but its true.

If you want fuel economy drive very gently in the first 2 gears and get a FMIC.

 

[bocean02]

FMIC? Sorry i'm not familiar with this term.

Thanks for the replies, I quite fancy converting turbos now!

The car has over 200k miles on the clock do you think this will effect the mpg?

 

[TooMany2cvs]

I have some how gotten 30Mpg in summer and now that its cold I get around 20Mpg and I have my fuel system running lean, these cars are not good on fuel not even the N/A are good on fuel, its a shame but its true.

<sigh>
Oh, well, that answers that question...

Now that I've got a working odo, I've put a number to my vague feeling of unease about the thirst of mine.

Tank of round trip from Herts to Norwich, plenty of 80-90mph, not much stop-start = roughly 25mpg.
Tank of half local commuting (country back lanes) plus half heavyish moving traffic m'way = roughly 20mpg.

(and they're big imperial gallons)
<wince>
Is there nothing that can be done...?

Thought - I've not had mine on an emission sniffer yet (MOT tomorrow...), but it's a Lucas '90 non-cat FPT with an AMM that's got "93 900" written in scrapyard-scrawl white paint marker pen on it. That'd be a cat car, so doesn't have manual mixture adjustment? It's got a big bright blue dot (plug?) on the top side - that should be the adjuster on a non-cat AMM, right?

I'm _really_ not looking forward to towing a loaded car trailer 500 miles in a week and a bit at this rate...

 

[TooMany2cvs]

FMIC? Sorry i'm not familiar with this term.

Front mount intercooler. Replace the intercooler (which you don't currently have on an LPT) from the normal position under the LH headlight with a much larger one in front of the rad. Cools the compressed air from the turbo a lot, allowing more power.

In theory, more power also means less loud pedal for a given speed, which means better economy. <hollow laughter>

 

[philb]

The lucas cat system has the same amm afaik. Mine had a cat, and still has the adjustment screw. The difference between the systems is in the wiring loom, so you should be ok. Adjust the amm in large steps and see what difference it makes. If you look up shadowworks threads you can see which way to adjust it.
If you increase the efficiency of the car, you may increase fuel economy. For example, a de-restricted exhaust will usually help economy.

Your car is not giving near what it is capable of in terms of fuel economy. On a run, my car will record between 32-35mpg, the best I've seen was 38mpg after a 100 mile journey at a steady 85mph. And it doesn't have an FMIC.
Around town, its between 24 - 28mpg, but normally 26-27.
There are plenty of threads about this, you need to get the amm setup correctly for a start and then see where you are.

 

[TooMany2cvs]

The lucas cat system has the same amm afaik. Mine had a cat, and still has the adjustment screw. The difference between the systems is in the wiring loom, so you should be ok. Adjust the amm in large steps and see what difference it makes. If you look up shadowworks threads you can see which way to adjust it.

Cheers.

Your car is not giving near what it is capable of in terms of fuel economy. On a run, my car will record between 32-35mpg, the best I've seen was 38mpg after a 100 mile journey at a steady 85mph. And it doesn't have an FMIC.
Around town, its between 24 - 28mpg, but normally 26-27.
There are plenty of threads about this, you need to get the amm setup correctly for a start and then see where you are.

<phew>

 

[cdaly]

FMIC? Sorry i'm not familiar with this term.

Front Mounted Intercooler. Cools the incoming air after it has been compressed (and warmed) by the turbo

The car has over 200k miles on the clock do you think this will effect the mpg?

It's likely that the oxygen sensor (if fitted) is out of spec which could affect mpg.

The simple way is to fit an MBC (basically an inexpensive valve) instead.

How is this different from just winding up the wastgate pressure?

 

[philb]

The wastegate will gradually open because of the boost pressure acting against the spring. Whereas some mbc's will not start to open until the required pressure is reached, which makes spoolup much faster ( too fast, as you've seen ). Winding up the wastegate by itsself will change the point at which it happens, but on a standard wastegate, you can't wind it enough to get serious boost, and you may also have problems with getting it to fully close, allowing boost creep.

 

[Honkey]

FMIC? Sorry i'm not familiar with this term.

Thanks for the replies, I quite fancy converting turbos now!

The car has over 200k miles on the clock do you think this will effect the mpg?

FMIC = Front Mount Intercooler

How hard are you driving? Are you warming you car up for more than 10minutes before going anywhere or something?

 

[unkleG'sif]

just for everybody's information, all LPT's (UK at least, seeing as that was one of only a few markets where there was such a thing as an LPT) came with Type 6 Primaries, which was the same ratio as a non turbo. This was to try and make up for a reduction in power, and to help with getting up to speed


all so-called FPT's (be it an "Aero", T16, T16s, Carlsson, Ruby etc) came with a Type 7 Primary, or the mythical optional extra, Type 8.....

the only reason i mention this, is to make clear (i didnt realise at first and was well pissed) that comparing an LPT to a true, factory "FPT" (not like my "Ex LPT"), is useless, as at 80mph my "LPT" is doing 4000+rpm, while my Ruby does around 3000 rpm..... and therefor usles a whole load less fuel

on a long run in my "LPT" i can only just get 28mpg (albeit with 3 passengers, and travelling to Le Mans - insert comments about hooligan driving )..... while my Ruby can cruise comfortably and get 32-34mpg.... its all down to the gearing more than the power and torque

G

 

[philb]

Yeah, I think the gearing makes a noticeable difference at 75-85mph, but under that, the lpt will not be much worse. I once got 30mpg in a week of commuting in my lpt, and it usually managed 32-33 mpg on long runs.

 

[Bawheid]

On our two Ftp T16's there is a noticable difference in fuel consumption, the car with type 8's generally gets high 20's and low thirtys on motorway cruising. The car with type 6's which is a considderably better runner consistantly getting mid 20's. There is quite a bit of difference but the car with type 6's is way more fun!

 

[Honkey]

Lots of NA saabs got type 7 primaries btw, mine does.

 

[unkleG'sif]

in the UK, all NA's got T6's AFAIK

probably different around the world (hence the clarification by refering to UK market)

G

 

[16saabs]

i actually got better mpg from a std 900 auto on 240mls journey than my t16 lpt vert 27 mpg on the vert, yet to fill auto but done 130 mls more at present . both cars together one following same run.

 

[bocean02]

FMIC = Front Mount Intercooler

How hard are you driving? Are you warming you car up for more than 10minutes before going anywhere or something?

I drive as sensibly as possible keeping under 2000rpm in lower gears in a vain attempt to save fuel. I have to check my bank balance before I hammer the throttle. It seems as though I should have probably gone for the bigger turbo. Maybe I will look to switch motors as it would be far more rewarding if I was being thrown into the back of my seat when I floored it, for the same price. Anyone looking to swap?!! What a fantastic car I have to admit, there's nothing else like it on the road but I should have looked into the different models and motors before I invested. Oh well so be it.

I am off work next week so will work further towards checking AMM, oxygen sensor etc. I got myself a Haynes manual but it appears to cover so many different engines, a bit more confusing than my old Volvo!

Thanks everyone, keep posting with more views (or if you want to buy a nice 900 )

 

[jameschong]

I am off work next week so will work further towards checking AMM, oxygen sensor etc. I got myself a Haynes manual but it appears to cover so many different engines, a bit more confusing than my old Volvo!

Thanks everyone, keep posting with more views (or if you want to buy a nice 900 )

I didn't notice any difference in consumption of my Lucas CU14 system after adjusting the potentiometer on the AMM. I believe the AMM resistance does not matter when the O2 sensor comes into loop. It might make a difference BEFORE that, but I have no proof of that. It might also not make an appreciable difference to the consumption as a result.

James

 

[16saabs]

what different engines , they are all 1985cc, 4 cyl, either 8v or 16 being the only major difference