Finding out how well your exhaust flows

[MrWilliam.Stewart]

Finally, an excuse to install a boost gauge on the asthmatic base model Yaris. You're a legend Jules.

[tiitsaul]

I made an O2 fitting adapter for this purpose. Steel brake line works well for this purpose.
My daily driver has 6psi of back pressure before cat at max load.
My track car, with custom exhaust, has less than 1 psi of back pressure.

[DZ_ZenDrive]

Your videos are just right on spot, appreciation from a vehicle dynamics engineer.

[grumpy.]

An interesting methodology, so simple.

[billstahler]

Still love your Autospeed writings. Another David Vizard but broader in scope and much more practical. Thank you ever so much . Mr. Julian .

[ratgreen]

Such a simple yet effective method of proving it, not sure why I hadn't thought of it myself to be honest.

Also, here before the: 'cars need backpressure' comments come flooding in

[vercingetorige]

illuminating, almost forgot we all have the hole for the lamda sensor pefecetly placed

[FilterYT]

Thanks, I just discovered your channel, great resource!

[michaely]

A vacuum gauge on existing inlet manifold fittings (post throttle plate) works to find BAD exhaust restrictions. You have say 15-20" vacuum at idle then as you increase revs to steady 2500-3500 the vacuum should remain similar say 14-18'. To prove it works stuff a big rag clamped in your exhaust end and run it again the vacuum will still be 15-20" at idle but now falls to 6-12" at 3000rpm.
Can do it in your driveway and no need to crawl under car and make new holes! ( turbo'd car may require you to disconnect boost pipe, or create a leak, to inlet manifold to ensure steady vacuum, i would only do that on turbo car in driveway testing not open road!).

[darksolara]

Wonderful as always… I'm a little stumped on how I would measure that with the hose coming off let's say with no meter in the car specifically for that… Every day driver shooting down the road etc.… So in my mind I'm seeing it attached underneath the car and then coming up the side of the car in through shall ..we say the window and then holding onto the mirror laying across your lap and such and then running down the road…?🤔 great book by the way....

[theshed]

The internal combustion engine operates on the principle of Delta P. Delta P is the difference in pressures between two points of measurement. Naturally aspirated engines only have 1 atmosphere of pressure to run on. The greater the restrictions anywhere in the system, the lower the potential Delta P.

[jamescuddihy]

It's interesting to see this when so many people are getting over pressure problems and blaming their too free flowing exhausts. It seems to me that manufacturers are speccing too restrictive components on the wastegate side (or maybe something weird with variable vanes) then using too much exhaust backpressure to tame the boost rise. Is that intelligent or lazy engineering?

Also which side of the DPF should we be measuring?

[timtrial]

This is useful for turbo and turbo manifold. Too much restriction here will push exhaust back into the cylinder and increase detonation and heat.

[johnmcdonnell]

Excellent Julian, as usual. What about the heat from the exhaust gases affecting the cheap pressure gauge?

[ELJ]

My car is straight piped with two catalytic converters and it flows better than ever I did it for fuel economy but got performance instead

[boudewijnb]

Wouldnt the airflow around the exhaust also have an effect on the pressure? The higher speed you go, the larger the effect, probably

[beyondpistache]

The man delivers yet again! Very interesting, do you block the exhaust fiting after testing, If so how?

[roflchopter]

How far does one have to get from the exhaust with metal fittings before one can switch to plastic/rubber? Does anything need to be done to protect the gauge from the hot gas?

[SMh]

I do it empirically, based on intake vacuum measure... 😊😅

[superbarnie]

What kind of hose would you put on the barb? Just typical rubber hose? I would think that would start melting pretty quick.