Turbo plumbing for a simpleton

[El Gringo]

17 minutes ago, Gixer1460 said:

 

@El Gringo- pressure is pressure and vacuum is vacuum whatever bore of pipe - only the response time is likely to vary although probably not as you could measure it reliably

That's what i figured, Ta

Edited May 4, 2018 by El Gringo

[bruteforce]

On 3-5-2018 at 1:38 AM, latheboy said:

Hi El Gringo,

How many pitot pipes do you have?

I have 3, 1 for the fuel reg and 1 each for 2 carbies into the overflow

Ø46.8mm ID up pipe and the pitots are Ø6.00mm each.

If you are getting ALL of your boost references from 1 pitot and spitting them over 3 places you might get problems.

I didn't drill my slides when I set mine up, Ø38mm carbs, but I did drill a hole to under the diaphragm .. Ø3.0mm I think... it's been a while.

To me It feels like the drilled slides are large part of the problem

I addition to the info of Mr. Latheboy; I had two pitots for the carbs in 1/4" tubing. My fuelpressure regulator was fitted tot he plenum, as it was on the XJ650Turbo.

[MeanBean49]

16 hours ago, Gixer1460 said:

Beg to disagree - Rising Rate regulators increase pressure based on their settings 1:1.2 or 1:1.5 and i've seen them upto 1:1.7 so for every 1psi boost the fuel pressure increases by 1.2 or 1.5 or 1.7 - as I said this is maybe not what the engine wants - sort of if more is good even more must be better!

A boost referenced FPR stays 1:1 so the FP stays exactly as it was without boost in relative terms - you are trying to achieve a constant fuel level in the bowl, how can that be accomplished if the FP is constantly changing compared to the boost pressure within the float bowl?

Re-reading an earlier post this " carbs with a FPR don't need vacuum " was badly worded. It should read " carbs do not need vacuum regulated FPR's"

@El Gringo- pressure is pressure and vacuum is vacuum whatever bore of pipe - only the response time is likely to vary although probably not as you could measure it reliably

I guess its just different ways we look at things. Rising rate like you describe wouldnt be any good.

Out of interest wouldnt an FPR like that need some sort of electronic control or be quite complicated to maintain a ratio not just maintain reference pressure + base?

Just wondering if somthing like that with a low ratio would work better than regular boost referenced fpr

[Gixer1460]

2 hours ago, MeanBean49 said:

I guess its just different ways we look at things. Rising rate like you describe wouldnt be any good.

Out of interest wouldnt an FPR like that need some sort of electronic control or be quite complicated to maintain a ratio not just maintain reference pressure + base?

Just wondering if somthing like that with a low ratio would work better than regular boost referenced fpr

No electronics..... https://www.fuelpumpsonline.co.uk/fse-sytec-adjustable-fuel-pressure-regulator-rising-rate-2072-p.asp

And for a carb - No, for the reasons outlined above.

[MeanBean49]

6 minutes ago, Gixer1460 said:

No electronics..... https://www.fuelpumpsonline.co.uk/fse-sytec-adjustable-fuel-pressure-regulator-rising-rate-2072-p.asp

And for a carb - No, for the reasons outlined above.

Ahh ok. Im just trying to figure out how they work. Got to be some way that they multiply reference pressure as it increases, not sure how that is done mechanically, maybe a tapered return or somthing.

I get the reasons, i was just thinking of a ratio of around 1.1, at high boost where it changes quickly just having a 2.5psi difference probably isnt enough to keep up with change. But if it was 2psi at tickover and say 5psi at 20psi boost would help running. Just a thought

[Gixer1460]

1 minute ago, MeanBean49 said:

Ahh ok. Im just trying to figure out how they work. Got to be some way that they multiply reference pressure as it increases, not sure how that is done mechanically, maybe a tapered return or somthing.

I get the reasons, i was just thinking of a ratio of around 1.1, at high boost where it changes quickly just having a 2.5psi difference probably isnt enough to keep up with change. But if it was 2psi at tickover and say 5psi at 20psi boost would help running. Just a thought

Not really as the float valve would see 5psi instead of 2psi - wouldn't stop flow so instant flooding. The pitot's shouldn't give any actual increase in pressure but if they were positioned say, on a section where the pipe flared out / increased dia. the pressure would increase fractionally. I'd say they are best positioned near the compressor to get the 'earliest' signal with most direct hose run of 6-8mm bore to maintain gas speed. Maybe this is why pipot installs show such wide variations in function and efficiencies? 

[MeanBean49]

37 minutes ago, Gixer1460 said:

Not really as the float valve would see 5psi instead of 2psi - wouldn't stop flow so instant flooding. The pitot's shouldn't give any actual increase in pressure but if they were positioned say, on a section where the pipe flared out / increased dia. the pressure would increase fractionally. I'd say they are best positioned near the compressor to get the 'earliest' signal with most direct hose run of 6-8mm bore to maintain gas speed. Maybe this is why pipot installs show such wide variations in function and efficiencies? 

Possibly.

I like my boost refference after the carb butterflies as I found if i had it before them i got flooding on closed throttle due to the plenum staying pressurised keeping the fpr open and fuel pressure high, but pressure in the float bowls drops due to butterflies being shut.

My turbo spools real quick so restores pressure when throttle opens quickly.

Guess its what setup works for your particular system

[latheboy]

So, it's been a few days now.... does it rev yet  

 

[El Gringo]

8 hours ago, latheboy said:

So, it's been a few days now.... does it rev yet  

Erm........ not yet, i was away racing over the weekend so didn't get chance to test it

It's all back in one piece now though so that's a start

I had a look at the breather system, i tried to separate the carbs to measure up for the plugs but they were stuck on one of the long bolts, so rather than break something i put them back together again. 1&2 and 3&4 are already cross linked by the vents so my blanking caps have the same effect as the plugs would. So I think they can stay as they are for now.

[Madb]

you haven't got time to go racing!  tap,tap,tap

[El Gringo]

Good Lord! An Update!

Progress, small but progress non the less.

Finally managed to find a suitable testing spot, so armed with a 12mm spanner and small screwdriver we gave it a go

I think it's still transition/fuel pressure related - the fuel pressure before definitely wasn't high enough so we wound it up to just under 3 psi with it running.

It's made it very rich at the bottom end but i guessed this would be the case

Gave it a run, second gear, and whilst it still stumbled at mid throttle crucially it eventually pulled through it and virtually revved out, and consequently scared the shit out of me.

So surprised was it that it had kind of worked i almost forgot to brake before hitting the main road! (which was also not very good having not bedded the new pads in) I also forgot to look at the boost gauge to see what it was doing

Few more runs, same result but getting worse for stumbling each time, interestingly it could be cleared by slipping the clutch through it

However, the fuel gauge was now showing no pressure despite not being touched, so i wound it up a bit further and the pressure came back, then went again.

I'm wondering if where i clipped the spring it's shifting inside the regulator causing it to fluctuate? Next step is to have the regulator back off and put the new spring in and see how low the pressure will go

[Madb]

Yippee! i thought ya got stuck racing. haha  Glad ya making some progress. seems ya find yer way bit by bit. shame ya didnt put a video clip up. would have love to here her scream! almost there, matey! 

[El Gringo]

14 minutes ago, Madb said:

Yippee! i thought ya got stuck racing. haha  Glad ya making some progress. seems ya find yer way bit by bit. shame ya didnt put a video clip up. would have love to here her scream! almost there, matey! 

Getting there slowly, completely forgot to take the Go Pro to film it!

Mind you it would have been fairly anti-climactic if i'm honest

[Madb]

a bike with a turbo on it will always be worth listening to! 

[El Gringo]

I might try and move the fuel pressure gauge to somewhere up the front then mount the go pro on the tank so i can watch the pressure and boost afterwards

 

[Madb]

Good thinking. you need to do that at least 5 times tho.

[El Gringo]

12 hours ago, Madb said:

Good thinking. you need to do that at least 5 times tho.

I'll have a look and see when I can get out on it next.

Going to strip the FPR later and got another idea to try too

If the next run is relatively successful it might be worth considering another trip to the dyno

[El Gringo]

That's interesting, stripped the fpr, no crap in it and the diaphragm is fine, then replaced the clipped spring with a new full spring.

Reassembled and put back on the bike, fired the pump up, that's odd, it's not showing any pressure?

I was under the impression that the Malpassi's were 5-6psi standard, so i wound the adjuster in and it took a good 3-4 turns to get it to just under 3psi on the gauge - not running at present.

Possibly more importantly, when I turned the pump off, the pressure remained on the gauge, which it didn't seem to do before.

I wonder if where i drilled out the return barb to increase the return flow/ reduce the return restriction is what has caused the base pressure to drop below the 5-6 stock psi?

In any case, i'll get it fired up asap and reset the pressure when it's running

[Reinhoud]

I just discovered this topic.. Nice bike to turbo.

 

I didn't read everything, but I read the bike choked at 6500rpm, is/was your plenum big enough? My bike had a bit of the same problem, turned out the plenum was too small, while someone who had a much smaller plenum had no problems at all..

[El Gringo]

On 9/13/2018 at 1:32 AM, Reinhoud said:

I just discovered this topic.. Nice bike to turbo.

 

I didn't read everything, but I read the bike choked at 6500rpm, is/was your plenum big enough? My bike had a bit of the same problem, turned out the plenum was too small, while someone who had a much smaller plenum had no problems at all..

Thanks boss, i think it should be okay, it's huge relative to the engine displacement, something like just under 4 litres if i remember correctly

 

I really need to get my finger out and sort this once and for all, it was pretty close on the last test run so i think another trip to the dyno before Christmas migt be in order

Edited September 14, 2018 by El Gringo

[Reinhoud]

59 minutes ago, El Gringo said:

Thanks boss, i think it should be okay, it's huge relative to the engine displacement, something like just under 4 litres if i remember correctly

 

I really need to get my finger out and sort this once and for all, it was pretty close on the last test run so i think another trip to the dyno before Christmas migt be in order

Still not running propperly?

 

Ignition timing ok? What brand spark plugs do you have? The manual for my GS1000 says Denso or NGK, but it runs like crap on Denso..

I think it's an ignition problem.

Edited September 14, 2018 by Reinhoud

[El Gringo]

1 hour ago, Reinhoud said:

Still not running propperly?

 

Ignition timing ok? What brand spark plugs do you have? The manual for my GS1000 says Denso or NGK, but it runs like crap on Denso..

I think it's an ignition problem.

I haven't tried it since i put a new spring in the fuel pressure regulator and made a choke stop so it may be ok now

Ignition timing is stock for now. Plugs are brand new NGKs

The choke springs are really weak so i'm thinking it's blowing them open, maybe partially, as it starts to boost

On the last test run with a big handful of clutch slip i did get it to rev past the stuttering point and pull pretty much up to the top end of the revs which is what makes me think it's a transition problem rather than ignition

Just haven't got a lot of time to test it

[El Gringo]

Aye up everyone

Bit of an update, decided that it was close enough to running properly to start pulling it apart for powdercoating/paint etc so i've got something to do over the winter 

So it's in bits and i'm just finishing up a bit of tidying up on the frame (and removing a snapped off drill bit from the side of the frame?! that came with the bike)

I've also been finishing up my 1216

[Gixer1460]

That's nice - not too shouty!

[El Gringo]

Bits all dropped off to the powder coaters - should have it back by middle/end of next week.

Might even be a roller again before Christmas!