Exhaust back pressure test - SE London (or near)

[IntriguedUser]

Hi all.

Sorry if this isn't allowed.

I'm looking for a garage/someone who can do a exhaust back pressure test either today or tomorrow around the SE London area. I have been to 6 garages and have been told cats on petrol cars dont go wrong or they're busy for 3 weeks.

Can anybody help, willing to pay.

Kind regards

[Decky_Q]

Probably because it's a very unusual request. Do you think your cat is knackered? Exhaust leaking or why do you think you need it done?

This would only really be done by exhaust designers or race teams. It is affected by all cylinders so would need to be plotted on a graph with very small time scaling, and would only be done to use the pulses from each cylinder to draw Exhaust gases from the next cylinder in the firing order.

If you tell me why you need it I can probably suggest a more suitable test for a road car.

[IntriguedUser]

Honda prelude 2.2

running very lean, supposedly 197bhp but feels in the 150 to 170 region. Lots of pinging and detonation under load in higher gears.

- no EML light

- Compression test 240psi on all 4 cylinders.

Reason for backpressure test is too see if there's a restriction in the exhaust ie a partially blocked catalytic converter.

I dont know where to turn really, I'm sure someone with a good scan tool that can show the values of different sensors would be able to pinpoint my problem straightaway however I don't know anyone.

Honda specialists are booked up 3 weeks ahead and I need the car

[untakenname]

Wouldn't a blocked cat cause the car to run rich as it can't breathe in as much air as normal?

Try unplugging the o2 sensor and then put a borescope tool in and have a look at the cat monolith, or take off the cat and take it for a quick run and see if it improves.

[Saudade]

If you have access to an infrared thermometer gun you could take it for a run and read the temps along the exhaust, internet suggests around 20-40 degrees Celsius difference between the input and output of the cat. Any more and it's likely blocked.

If the cat is completely blocked then I would expect it to run rich (more fuel going in then air getting out) so I'm unsure if it is that.

I suppose the lean mixture could result in misfiring and therefore unburnt fuel getting into the cat and damaging it... but then the problem isn't the cat.

[Fleckers]

I would suggest a tuning shop like Sanspeed in bexleyheath or even torque developments in barking

[t400ble]

Infer red gun is a good shout

[IntriguedUser]

I'm booked in to get the cat replaced on thursday.

Here are a few more symptoms:

- bogging

- car feels like its slowing down itself, as if a caliper or handbrake is stuck but everything is moving freely.

- if I hold the speed steady at say 20mph the car feels like its lurching, then trying to go, then lurching. Not enough to cause a massive jolt but enough to feel. This yoyo effect is more noticeable in 1st and 2nd gear.

I'm wondering if the timing may have jumped a tooth. Or possibly a fueling issue. No codes, vtec still works car still reaches the factory redline of 7800rpm.

I'm going to get the cat replaced and then take it to a specialist to do some diagnostics. I will let you guys know the outcome.

Cheers

[Saudade]

Sounds like it's either a fuelling issue or something wrong with the throttle body.

I'd try cleaning the throttle body and the IAC valve then look into the fuel system, probably starting with the fuel filter and then injectors.

It might be the dizzy if it's not the fuel system.