4722 replies to this topic

[Nev]

Some eBay stuff turned up in the post today. This allowed me to screw a bung into the lambda sensor bung with vacuum pipe leading out of it to a PSI gauge in the cabin. I started the car up and was rather surprised to see 0 PSI of back pressure at idle (1000 RPM).

 

I let the car warm up a bit and then revved it to 4000 RPM and had 0 back pressure reading! Abeit the needle on the gauge was twitching just off the 0 PSI needle stop and the turbo doesn't spin up when there is no load on the engine.

 

This is awesome news and thankfully ratifies my design and gas flow logic, hopefully my openly published R&D will be of some help to other people. From what I've read, most ordinary street cars at idle would expect roughly 0.75 to 1.25 PSI of back pressure, leading up to about 4 to 8 PSI at high revs.

 

Can't wait to take the car out for a full bore blast when the fog and dampness clears and see what the back pressure reading is.

 

I have to admit, after the doubters on here I was beginning to wonder if I'd messed up the design myself, particularly with reflection wave pipe. This morning I had already drawn up a further design including straight through (external flapper bypass valve), an extra resonance chamber and an adjustable (external) helmholz pipe. Thankfully (so far) it seems this won't be necessary now.

 

Hoorah.

 

Edited by Nev, 16 December 2016 - 07:36 PM.

[oakmere]

Very surprised by the results but good news 👍

[The Batman]

Have you burnt the wadding away already? I joke Great news

[Nev]

I'm of kayak surfing for 3 days now, but can't wait to get back and test it on full bore.

Edited by Nev, 17 December 2016 - 12:01 AM.

[oakmere]

To cold for surfing unless your off to Hawaii

[Nev]

To cold for surfing unless your off to Hawaii

 

Cornwall, lovely in a dry suit. The winter swells are picking up, 7 to 10 foot down at Constantine Bay over the next few days.

 

Far nicer in winter TBH, when the whole 3 mile stretch of beach is empty of "image surfers", with just you, the sea and communing with nature.

 

We are wearing cams, will try and post up some videos. Here's a video from the summer when the waves were small (turn the volume up please, my cam is poor at recording it):

 

Edited by Nev, 17 December 2016 - 12:12 AM.

[Nev]

Have you burnt the wadding away already? I joke Great news

 

I think it is already starting to disintegrate with just 80 miles of use, as the exhaust note sounds a bit different.  

Edited by Nev, 17 December 2016 - 07:48 AM.

[Nev]

A shot from today, this was only a 6 footer, but we surfed some 10 footers too:

 

Edited by Nev, 17 December 2016 - 07:46 PM.

[The Batman]

SHARK!!!

[oakmere]

That's not 🏄

[hairy]

Nev - how do you pull a wheelie on a surf ski?

[Nev]

Nev - how do you pull a wheelie on a surf ski?

 

By doing about 25 mph down the face of the wave - very exhilarating!  Sometimes we go so fast that we even cartwheel down the steep faces.

[FLD]

Looks like great surf! Always worth getting kitted up to avoid crowded beaches. Sent from my iPhone using Tapatalk

[Nev]

In this video you can see how my friend get "ejected" from an 8 foot crashing wave:

 

https://youtu.be/8SktW66WfzI

Edited by Nev, 19 December 2016 - 09:52 AM.

[Nev]

Always worth getting kitted up to avoid crowded beaches.  

 

Indeed, though crowded beaches in the winter is not a problem, all the fashion/image surfers are nowhere to be seen. All I saw over the last 2 days was 2 other sufers in the water.  

[KurtVerbose]

That's why I go to Alaska for surfing. No crowds and big waves as the glacier ice falls into the sea.

 

[Nev]

Managed to get out and do a lilttle bit of testing, under acceleration I got the following back pressure figures:

 

2000 RPM = 0 PSI

3000 RPM = 0.5 PSI

4000 RPM = 1.5 PSI

5000 RPM = 4.0 PSI

 

Couldn't get any more revs in the greasy Xmas shopper conditions. I've got a suspicion it will flow badly at high revs now.

 

Maybe design #6 or #7 will need to be made.

Edited by Nev, 20 December 2016 - 11:24 PM.

[Dan r]

That's high and turning into a very steep curve, hope the next design works out. Got to be challenging trying to run wot tests this time of year!

[FLD]

Do you need to log it against rpm and throttle position? I'd have thought wot and low rpm will give a large flow requirement too. Sent from my iPhone using Tapatalk

[Nev]

Do you need to log it against rpm and throttle position? I'd have thought wot and low rpm will give a large flow requirement too. Sent from my iPhone using Tapatalk

 

Yea, throttle position makes a huge difference to the back pressure (once over 4000 RPM), mainly as the V.E. (and hence gas volume) is increased from about 95% to about 235% by the turbo.

 

Also, as you guys say, it is bloody hard to keep an eye on the RPM and the PSI gauge and take accurate readings. I may need to employ a passenger to read the PSI gauges whilst I drive.

 

Until I can record the PSI at 6000, 7000 & 8000 RPM, I won't know for certain, but the rising rate of the back pressure to RPM is looking worrying. I see 2 possible reasons for this:

 

1. Deliberate design of the reflective wave pipe causing too much restriction.

2. Sheer lazyness of not making the complex merge collector for the tail pipe exit when I built it.

 

Edited by Nev, 21 December 2016 - 10:07 AM.