Air/Fuel Ratio gauge, anybody fiited one to turbo

[diabloam]

Just bought a new one of these (RaceX) off ebay, but obviously need to fit, has anybody got one on, or have fitted one. Thought it be a good precaution to fit this and a more accurate boost gauge before I start upping boost etc.

Am assuming my '86 944 Turbo has neither a cat nor a lambda.O2 sendor, so probably looking at getting one and welding a boss into exhaust. Has anybody done this to there car, where is best place to site it on exhaust etc. Also know they need a heater wire feed to operate. Any advice or people knowledable about this subjest please lend us some tips, I know I need to get right sensor and position it carefully as think the voltage signal from these sensors is very variable round the stoichiometric ratio and want to get a reliable gauge and sensor set up so cant be confident I aint going to run lean at higher boost rates, they also look quite cool which is a bonus and at least I will be able to justify having it, unlike plenty boy racer out there who fit this kinda crap for no reason.

Cheers for any help, hope I aint annoying everybody on forum with my incessant posting asking for advice, I'll settle down once know car inside out. Besides I am offshore and am sitting in front of the internet all night shift as we aint drilling the now so loads of time to play on forum, thanks again for any help
Diabloam

 

[Diver944]

Later cars had a cat (and lambda sensor) as standard, and US cars have always had them so there is a bung already present in the crossover pipe leading to the turbocharger. However if it has never been used it is a bugger to remove the bung and it is in a pretty difficult place to get to in situ. If you search back a couple of years I think there was a post from John Sims about his bung difficulties.

Others have had bungs welded in to the crossover for a narrowband sensor, but my wideband sensor has been placed after the turbocharger downpipe. I can't remember why now [&:], but there was a specific reason.

 

[John Sims]

ORIGINAL: Diver944

...........If you search back a couple of years I think there was a post from John Sims about his bung difficulties....

'Twas a complete pain in the bum and wouldn't come out no matter what. I gave up and subcontracted to my independent who melted a tool trying to heat the bung and remove it.

In the end we had to replace the whole cross over pipe with one that had a bung you could get out.

If you buy the Porsche lambda you can plug it straight into the loom and then pick up the signal from the DME plug - much easier than trying to drill a convenient hole through the bulk head.

I'm happy that narrow band is better than nothing but wide band is far more useful (another thing on the wish list but don't tell Belinda)

 

[Guest]

I use a Zietronix wideband. I had to get a bung welded in but as I am using a cat delete there was never a bung there anyway!
My Zietronix has datalogging and also monitors my exhaust gas temperature and boost pressure.
Great kit and well supported

 

[sawood12]

The crossover bung is no good for a wideband anyway as the temps are too hot. It needs to be after the turbo. I've just had a bung welded in on the down pipe just after it turns from the vertical to the horizontal - about just before the cat if I had one. I think that is a good posistion - you get less moisture there than you do down stream and the wideband sensort don't like moisture. The temps after the turbo are OK for the sensor. Just need to fit the rest of the kit and get it working now.

 

[diabloam]

Well my car is an 1986 uk sold car so not entirely sure I even have a bung, and away the now so cant check. But I suspect not given its age. So guess I am looking at having to weld a boss in and fitting, hopefully a wideband sensor although a narrow band is ok for just checking safety in term of fueling right, although it be no good for mapping or datalogging. However I aint really bothered by that, just what to be able to see if I am running lean or not, which a narrowband sensor should manage (aint sure of what the gauge requires, will find out when it arrives).

In terms of a place in the loom already existing and a feed to the DME I have couple of questions. Do all 944 Turbo wiring looms have this in place. Also mine is probably the lesser number of pins DME, were these extra pins to do with later emissions control (cat, O2 sensor) or what are they for. I am thinking of wiring it independantly, with a cheap new sensor from ebay or off a breaker, will weld a boss in myself. Any good holes on the bulkhead that can be used to run extra wiring already there and where, assume there is as usually is, even if its beside existing wire grommets.

Also I remember reading I can tap in to a hose in the passenger footwell for my boost gauge, rather than run pipe through bulkhead. Is this a pressure pipe going to the DME which allows it to measure boost pressure, what size is it (i.e. so can order a T-piece and length of pipe) before I get home, thanks guys

 

[sawood12]

I think the pressure tap to the KLR computer is measuring manifold pressure. Now i'm not sure what is the 'correct' way to do it as i've got mine connected from the IC output banjo bolt which will give a different reading. Under partial throttle the pressure could be higher before the throttle body so you wont be measuring max boost pressures if you connect your gauge to the KLR pressure line. This will be higher pressure unless you are at WOT and even then you might get some pressure drop across the throttle body butterfly.

I don't really know if i've got my boost gauge hooked up correctly now. I just set it up as i'd seen it set up in other cars not really thinking about it.

 

[diabloam]

Hi there, have been doing some interesting reading on the Lindsay-Racing on the internet, sure you all know about the site, but they are defo 944 lovers thats for sure. Thier guide I found for fitting a boost gauge uses the pipe that goes to the KLR, reading vacuum in the manifold as well, since this hose come from inlet manifold and it obviously see vacuum as well as boost, when throttle is closed. I reckon the largest pressure drop after the compressor is going to be the intercooler and dont think the drop across the throttle body will be particularily big. I also reckon tapping in here has a couple of benefits. I reckon you will then be reading the boost pressure the engine actually sees which is in reality the one I am going to be interested in, and also be reading the one that the KLR recieves. Also it saves running a long length of hose into engine bay which is a plus. The gauge I have got reads vacuum as well so I hopefully wont have a problem, then again this is the first turbo car I have owned or going to (dont think my old turbo deisel range rover counts, its a very straight forward setup) be working on much so I could be wrong, whats the common consensus with everybody, tap in to hose going to KLR in passenger footwell or look to running a hose through bulkhead and attaching somewhere in the lines in there. Please correct me if I am heading down the wrong path. Also what is the gauge of the hose in the footwell so can order some and a T-piece, cheers

 

[John Sims]

You want to be reading boost pressure at the manifold so the pipe to the KLR is fine. Or you can T off the fuel pressure regulator feed or any of the the other feeds off the manifold. If you can get a Laust manifold you are laughing.

Reading off the inter-cooler banjo bolt will give maximum boost pressure as, one assumes, your throttle will be fully open and therefore give an unrestricted pipe to the manifold. It won't read manifold vacuum though, (as already noted) and it may give introduce latency in the operation of the waste gate as the gauge will act as a damper to the pressure signal.

 

[Diver944]

I was always a bit wary of feeding off the KLR line because that is the one line that the ECU uses to see boost pressure and you don't want to increase the risk of leaks or problems there, plus it is a very thin, brittle nylon line and I think a tee piece would not be easy to find.

I tee'd into the vacumn reservoir line that comes from the manifold, along the firewall to the space above the drivers wheel. There is a handy rubber grommet just by the clutch reservoir that leads straight to the drivers footwell and excellently placed to run the pipe to my gauge by the gearstick (or to an A-Pillar gauge)

God my engine looks awfully mucky in that old pic [][8|]

 

[sawood12]

THanks John - you've set my mind at ease as i've T'd in to my gauge off the FPR so sounds like i'm OK. My gauge does read vacuum perfectly well so sounds like all is well.

 

[diabloam]

Good stuff guys, not sure where to tap in now, sawood, where exactely do you have yours taped in, am unclear exactely where you mean. I think i will see what nick the pipe to the KLR is in and play it by ear from there. Diver, good pic, do you get clear and reliable readings of vacuum and boost there no bother. In reality there is quite a few places you can tap into, just trying to figure of where is best for me. That grommet sounds handy for getting cables in and out of interior, awkward to get to?, is it an upside down in the drivers footwell job?
cheers

 

[Diver944]

ORIGINAL: diabloam

Diver, good pic, do you get clear and reliable readings of vacuum and boost there no bother.

Yes no problem. I think any of the pipes that are connected to the manifold will do just as good a job, I picked that one because it connects to the blue valve and meant I didn't have to actually cut anything. It is useful being able to see the vacumn as well, once you get used to your individual readings then it is very easy to see when you suddenly have a leak. My vacumn noticeably increased once I had a new engine fitted