DIY WB exhaust clamp - anyone?

[Bubba Zanetti]

I don't know if this is really right place to ask - but it's definitely related to tuning, so here I go - has anyone made custom exhaust clamp for WB sensor insertion in exhaust pipe , something like this :

http://www.innovatemotorsports.com/xcar ... 250&page=2


Is there any posibility of wrong AFR reading with turbo setup due clamp location that is far away from "ordinary ", much hotter position ?

If I understood correctly , WB controller has internal thermal compensation circuit but I have to be sure .

What about mixing outside air with exhaust gases - how to prevent this, Innovate clamp has closed pipe on the end where sensor mounts and has hole on the bottom...

I know that similar clamps are used in dyno shops without problems but is there something special involved in designing such clamp or I can just , let's say, weld oxygen sensor nut purpendicular on piece of 1" pipe, about 30cm long and just put it in muffler - and start tuning without worrying that my mixture isn't correct?

Or I must use something similar as on Innovate link above :"...Patent-pending, Venturi-effect..." - hmmm, that sounds very much like some marketing trick for such simple device....

[PSIG]

... has anyone made custom exhaust clamp for WB sensor insertion in exhaust pipe ... is there something special involved in designing such clamp or I can just , let's say, weld oxygen sensor nut purpendicular on piece of 1" pipe, about 30cm long and just put it in muffler - and start tuning without worrying that my mixture isn't correct?...

Do your thing. I once saw a very well funded road race team use a hose clamp to attach the sensor to a heavy wire (coathanger) and shove that puppy up the tailpipe for tuning. They used a half-hitch to hold the wires around the tailpipe and ran the rest to the controller. Hi-tech stuff there... I never got a reason why they did this maneuver but I assume it was to verify the primary sensor's accuracy.

So long as it't far enough up the pipe to eliminate reversion (at least a foot or so) and be aware the reading will severely lag the actual engine events, which is the biggest drawback to this type of setup. Personally, since it's so easy to add a threaded bung further up, it's hard to justify a tailpipe setup.

David

[cdallacosta]

I have.

Mine is a ~4 cm long, 1,5 cm diameter tube connected to a small box where the sensor plugs in and with a hole on the other side a tad smaller than the tube. There's also a tab to lock into the tail pipe.

Works pretty well and lag is minimal. The sensor is temperature compensated so readings will be correct, and when it's reading free air you'll know since it'll be reading something impossibly lean.

I don't know about that Innovate clamp but the small tubes look like they'll create a lot more lag than a simple tube.

[Bubba Zanetti]

PSIG,

I know it's hard to justify this tailpipe setup with clamp , especially for tuning two cars max, but soon I'll have to install Megasquirt in few more vehicles and some don't have already welded bungs - after little thinking , it seems easier and more practical just to attach exhaust clamp from car to car then welding bungs in awkward positions under car and drilling or finding suitable holes in floor for attaching wires...

So, I have some first CAD sketches - can this simple welded pipe work?

http://img.photobucket.com/albums/v358/ ... _CLAMP.gif

On this drawing , pipe is closed (welded plate) on the WB sensor end, and little hole is drilled under for exhaust gases to escape - or maybe that hole isn't necessary at all?

I left out clamping system on purpose - I just don't like Innovate system with only one bolt for attaching - it is simple of course, but somehow seems slippery and unsecure - and I don't like idea of de-attaching & losting WB sensors down the road - maybe some ordinary muffler clamp slightly modified will serve better for that purpose, I'm not really sure

[cdallacosta]

Bubba, the sensor won't fit in the pipe the way you designed. (Unless you are using a very large pipe which might not fit smaller exhausts)

You need a small "chamber" to fit the sensor - weld the pipe to that and make a hole on the opposite side.

[cdallacosta]

Bubba, the sensor won't fit in the pipe the way you designed. (Unless you are using a very large pipe which might not fit smaller exhausts) You need a small "chamber" to fit the sensor - weld the pipe to that and make a hole on the opposite side.
-------------------- m2f -------------------- This post is at: http://www.msefi.com/viewtopic.php?p=135430#135430 -------------------- m2f --------------------


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[Bubba Zanetti]

2 cdallacosta:

Tnx for advices, I made my clamp version yesterday and made one chamber where WB mounts , inlet is steel pipe about 10cm long and 15mm OD, and on the chamber outlet I drilled 8mm hole.

Today my friend and I tried clamp on his 1600 turbo engine - first thing that I noticed is that under 2200 - 2300 RPM there isn't enough exhaust flow - WB reads free air (>18.9:1 AFR on Megatune window), but going over 2300 RPM and readings seems OK and WB follows combustion pretty well - going from 10 - 11.5 AFR on 0.4 bar boost.

As you said, lag is minimal.

I only hope that readings are correct - it's a high compression turbo engine (9.3:1 CR)