Bunkey's Fast Road/Race Development Diary

Bunkey · **Posted:** Sat Jul 25, 2020 5:02 am

I'd rather avoid discussing legalities tbh, I appreciate it's a topic which some people might find insightful but I just want to be able to document my work without feeling anxious about what I'm posting or appearing hypocritical.

If people are looking to emulate anything here then I trust they have the sense to research and understand the ramifications.

SlackGarry · **Posted:** Sat Jul 25, 2020 12:00 pm

Bunkey wrote:

I'd rather avoid discussing legalities tbh, I appreciate it's a topic which some people might find insightful but I just want to be able to document my work without feeling anxious about what I'm posting or appearing hypocritical.

If people are looking to emulate anything here then I trust they have the sense to research and understand the ramifications.

Totally agree, You wont stop posting will you ?

Love to read what your doing.

Thanks mate.

PetrolDave · **Posted:** Sat Jul 25, 2020 3:33 pm

SlackGarry wrote:

Totally agree, You wont stop posting will you ?

Love to read what your doing.

I 100% agree, it's great work which is telling us all so much about these little engines.

SlackGarry · **Posted:** Sat Jul 25, 2020 5:13 pm

So true Dave..

MPJ · **Posted:** Sun Jul 26, 2020 1:20 pm

Hmm, on the removing the second lambda discussion, would I be correct in saying that if you put about a steady 4v across the signal wires then you wouldn't get an error code thrown up on the dash?

Keep posting Bunkey, we're all grown ups and your diary is really interesting - lots of useful tips and insights, even if you're not planning to race your Bug :-)

Fredrik M · **Posted:** Mon Jul 27, 2020 9:27 am

Bunkey wrote:

This will be my next mod, bike muffler for a Suzuki TL1000 in titanium.

Will try to fit it during the next 5 weeks.

Bunkey · **Posted:** Tue Jul 28, 2020 1:32 am

MPJ wrote:

would I be correct in saying that if you put about a steady 4v across the signal wires then you wouldn't get an error code thrown up on the dash?

That seems plausible. I'm not exactly sure how the lambda sensor relays information and haven't traced the circuit but mine has a black, a grey and two white wires coming from the pins. My best guess would be a supply, ground and two signal wires - If the sensor varies the resistance between these signal wires to transmit information then you could measure that resistance on a functioning setup and connect a resistor in leau of the sensor, possibly; else it'd be tapping an auxillary power supply using resistors set up as a potential divider to get your ideal voltage.

I don't mind refitting the sensor for an MOT as I'd have to replace the manifold/cat anyway; would sooner just take the check engine LED out of the dash if it was bothering me :lol:

That's a neat workaround though.

Fredrik M wrote:

This will be my next mod, bike muffler for a Suzuki TL1000 in titanium.

Nice, I picked up a bike muffler from a scrap pile last year but it turned out not to be straight-through so I never put it on the car.

Convenient link to today's efforts though...

Bunkey · **Posted:** Tue Jul 28, 2020 2:43 am

I got hold of a used Sportex exhaust over the weekend.

I've never really been a fan of twin tips or centre exits but the silencer is a straight through type and used by the recent CityCar Cup series so it has some pedigree at least.

After a bit of hunting through scrap bins at the local garages I came across some suitable 38mm pipe and set about modifying it more to my taste...

It was pretty scary cutting up a new purchase :shock:

The gasless welds aren't the prettiest but they do the job.

I had a bit of a race on this evening getting it back together and high-tailing it over the Pennines before last orders at the pub where a friend of mine was staying for the night :lol:

It sounded absolutely epic on the way there though, much racecar. I find it a huge improvement over the standard twin tip, it's less of the warbly 'trying to be something its not' and more just no-frills rally car.

It'll flow better than the standard 180-degree-bend pipe too.

I gave it a lick of paint before it went on, to keep the rust at bay.

I'll try to put an audio/visual update together tomorrow.

MPJ · **Posted:** Tue Jul 28, 2020 12:40 pm

I think that the second lambda on the Bug is a standard four wire zirconium unit, so it'll be 2 x signal and 2 x heater wires. It sends a voltage back which varies, depending on the oxygen content of the gases. The heater circuit just helps it get up to operating temperature quicker. From what I've read, the Bug will be looking for 4 to 4.5v from the sensor in normal running, so if I can spoof that it will be happy that everything is okay. I've used a series of diodes before to get a desired voltage drop, generally about 0.7v per diode, so would probably need 14'ish to get down to 4 to 4.5v or use a resister as you say. Could just try 3 x AA batteries (to provide 4.5v) in the first instance as a quick and dirty proof of concept. I'm due a (delayed from April) MOT, so will get that renewed first and then experiment. Have had a look at the sensor and it's well and truly seized in the exhaust pipe - was yours like that? Any suggestions based on getting yours out?

Bunkey · **Posted:** Tue Jul 28, 2020 3:26 pm

MPJ wrote:

to get a desired voltage drop, generally about 0.7v per diode, so would probably need 14'ish to get down to 4 to 4.5v or use a resister as you say.

That is novel Haha.
If you're set on using diodes, red/blue/white leds have a Vf of ~2-2.5v depending on the batch and colour. I design and build amplifiers & effects for musicians in my other life and whilst you're not dealing with small signal audio, a chain of 14 diodes sounds like a nightmare! You would also need to include a current limiting resistor or they wouldn't last long. V=IR

Quote:

Had a look at the sensor and it's well and truly seized in the exhaust pipe - was yours like that? Any suggestions based on getting yours out?

I just soaked mine in WD40 for 10 minutes and gave it a few taps with a bar and hammer to free it up first but it did require holding onto the front crash structure and using my foot on a big adjustable spanner. The torque setting is 44lbs/ft iirc but yeah they get pretty firmly welded in place with particularly dry thread from the heat.

Citroen C1, Peugeot 107, 108 & Toyota Aygo Owners Club. (Discount code for CityBugStore: C1OC)

Bunkey's Fast Road/Race Development Diary

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