SBD208: air sensor

[StephaneM]

Hello,

I fitted my SBD208 kit on my Vx. I tuned the flaps potensiometer & fuel pressure as it as to be. I installed 4 new spark plugs & now it starts on 4 cylinders. But it is not very "round"... so I have 2 questions:

- is it normal that with this kind of kit, the engine idles not very good when the engine is cold?

- wich air sensor as to be used with this kit? Is it the serial Vx one? or not? what is exactly the influence of this sensor?

Thanks in advance?

[StephaneM]

In fact, I already asked this question by e-mail to SBD but I don't have answer after one week... I would also like to know if iy is very sensible regarding balancing (what is tuned with a synchrometer...)

 

[Chelspeed]

No this is not normal, idle should be very smooth.

 

By air sensor I presume you mean air temperature rather than the air pressure sender more normally called a baro sensor? If it's air temperature then SBD normally sell a sender with their kit, I think it's Vauxhall but wouldn't swear to it. It looks very similar to the water temp sender but has an open end with 5 holes in it and the actual element is visible inside the end. You should be able to use any air temperature sender as there is a calibration curve within the software to map sender voltage to temperature.

 

The air temperature sender lets the engine change the amount of fuel injected to the engine as the air density changes with air temperature. On a really cold day the air will be denser so more oxygen will get sucked into the engine on each stroke, the air temperature adds more fuel to allow full use to be made of the extra oxygen.

 

I'd ring SBD, +44 208 391 0121, they are very helpful on the phone but they do get an awful lot of emails so I guess some will slip through the net every so often.

[StephaneM]

Thanks for your reply!

I have 5 holes at the end (4 on side & 1 in front), I think my sensor should be OK... here it is:

http://stefanauto.chez.tiscali.fr/RQ/picture2.jpg

After the second try, it idles much better...

I wait the road test in one or two days...

cheers

 

[Chelspeed]

Yep that's the same as mine, air temperature. Usually mounted in the back of the air filter to measure the tempearature of the air entering the engine.

[stu999]

- is it normal that with this kind of kit, the engine idles not very good when the engine is cold?

---

 

I had always assumed that poor idle when cold wasnt an issue because even though the ECU can alter air/fuel ratio to compensate for a cold motor, it has no way of self regulating the idle speed.

 

I know that a lot of modern bikes with fuel injection have a 'choke', but in reality it is merely a device to raise the idle speed until the engine warms up sufficiently.

Unless the setup includes a idle control valve, the 'poor idle when cold' scenario *may* be expected?

 

Still learning...Stu.

 

Sex is alright, but you cant beat the real thing......

[Nick Pargiter]

Stephane

 

"Tuned with a synchronometer" This means you have to balance the air flow into each cylinder by adjusting the buterfly in the throttle body. You need the same amount of air entering each cylinder for it to be balanced. Check out Demon Tweeks, they sell them. Also from what I remember the map supplied with the 208 kit does not include a cold start programme. This may have changed but was the case a few years ago.

 

Nick

 

Mellow Yellow Vauxhall - I don't think so!!! 😬 😬

[16vastra]

it now has cold start, if the idle wavers thats probably the TBs being out of balance (get carb synchrometer from halfords)

the air temp sensor is a vaux/Bosch part, used on the LET engine

make sure you have the throttle pot reading 0.33v with the throttle stop screw out, then wind the throttle stop in till the laptop just starts to show 0.37v as this is crucial to it idling from cold and giving a nice 'on/off' throttle feel instead of a jerky throttle

[StephaneM]

Thanks for all your answers

I'll try all this work this week & I'll let you know the result...

If you are interested by my work in progress:

 

http://stefanauto.chez.tiscali.fr/RQ/init1.JPG

http://stefanauto.chez.tiscali.fr/RQ/init2.JPG

http://stefanauto.chez.tiscali.fr/RQ/cat2209-1.jpg

http://stefanauto.chez.tiscali.fr/RQ/cat2209-2.jpg

http://stefanauto.chez.tiscali.fr/RQ/cat2209-3.jpg

http://stefanauto.chez.tiscali.fr/RQ/cat2209-4.jpg

http://stefanauto.chez.tiscali.fr/RQ/cat2209-5.jpg

 

cheers.

[StephaneM]

Here is the answer on this subject from SBD (thanks SBD!):

"I know the hose that you describe which is missing from the Caterham, although you can block off the outlet from the manifold, I would always advise if possible that this tube is fitted and you alter your cooling system to suit it and then refit a thermostat to your engine. We produce a special low temperature thermostat, part number THERM-70 £30.00 +VAT."

If I well understand, It is not necessary but advised and if fitted, it's better to install a low temp thermostat...

Question: If I don't fit it, Is it better to also use a low temp thermostat?

(In fact, I won't use very high revs on my engine till I don't have a dry sump. In addition, I have to discover the car, so I don't think I willl overheat in next few days. I will do all this work this winter with a smaller alternator, installation of the return in this famous pipe I took away, dry sump... but now, I have waited for 6 months, so I WANT TO DRIVE MY CAR ) 😬 😬

 

Cheers

 

Stéphane