late boost

[Trip]

During my hillclimb race I was always coming off boost exiting slow chicanes and kept pressing the clutch to get some revs/boost up.

After analyzed data collected from the runs i noticed that my max boost which is currently set to 13psi is coming at an average of 5000rpm. This is very late in my opinion and I have a small turbo to eliminate such delay. I also noticed that once i reach the target 13psi, boost plays up between 10psi and 13psi to redline.

I conclude i have one of the following:

Boost leak from turbo to engine.
I have pressure tested the system and am not sure what i should look for. It was slowly leaking from the throttle bodies area. slowly i mean 25psi to about 5psi in around 20seconds. I am running without BOV too.

I am controlling boost using a manual boost device (not bleed valve), its barley doing work as the actuator is a 12psi spring (or should be). Could it be this is set too loose and delaying my boost ??

I could also have an exhaust leak between engine and turbo, visually i am not seeing any exhaust coming out from the front and noise wise its sounds ok too..

I am not giving it enough boost.

what else should i check for ?


Apart from that the engine runs absolutely fine.

My setup
GT2871R (the small version with housing identical to standard turbo)
ARC TMIC
Japspeed manifold
AM downpipe/elbow
Field ECU




here are my 3D plots from my datalogger

Column is RPM x 100, Row is PSI,

EGT



AFR



PSI

 

[stumo]

If you'e got a leak then that's not going to help (either on the exhaust or inlet side)

What manual boost controller are you using? try removing it see if it makes any difference to what revs it starts to make boost and if it stops the boost playing up between 10 to 13.

If you're using a dawes device then take it apart and check that the ball is free to move. set the boost with it off the car.

If your ign timing is retarded that will slow down the production of power/boost.

you could try upping the pressure that the controller is set to, don't use all the boost (especially if you haven't mapped for that much boost) but it might allow the turbo to boost earlier.

 

[Trip]

Manual boost controller is http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=220541176033

The ECU is a field ECU similar to mines and blitz, it can take 1.2bar on standard turbo, but since i am running a GT2871, i kept boost low. I will try and gradually increase boost up to a decent AFR level. I will try bypassing the boost controller too.

My first thought was i got a leak somewhere on the inlet side but car does not suffer from high idle, and it generates around 10psi of vacuum on idle. maybe i have the exhuast side which is leaking. i will recheck.

If i have timing off by few deg, would it effect boost that much ? as i said, car is running fine.

thanks stumo

 

[John]

Im also running a 2871r trip and my peak boost is coming in at 5k rpm, however im achieving 13psi at 4k rpm but im running a stock manifold unlike you.

So from this there is obviously an issue somewhere, have you checked the exhaust turbo gaskets, I had an leak there and seems to be a common one?

 

[Animaldaz]

I'm not sure if this has any significance but I am using the same mbc but on a standard hybrid turbo with no late boost issues. Mine holds 14psi perfectly

 

[Trip]

So from this there is obviously an issue somewhere, have you checked the exhaust turbo gaskets, I had an leak there and seems to be a common one?

Was the leak evident visually and how much did it effect the boost delay ?

 

[Trip]

I'm not sure if this has any significance but I am using the same mbc but on a standard hybrid turbo with no late boost issues. Mine holds 14psi perfectly

A friend of mine is using one on a cossie and he never had problems with it either. its a very simple device which looks like it should work

 

[John]

Was the leak evident visually and how much did it effect the boost delay ?

It could be heard, although because the car is loud it took some time for me to notice. Hard to put a number on it but it didnt spool up as quick and peak boost was slightly down on where it should have been.

 

[RO_SUNNY]

Your problems might be:

-Pressure leaks in the system
-Actuator diafragm punctuated and leaking pressure
-Actuator not working properly
-Manual boost controller -->IF I WERE YOU, I WILL BIN IT IMEDIATLY AND GET AN ELECTRONIC ONE!!!!!!!!
-Incorrect electronic setup

These are basicly the things that can go wrong.

Please take this an advice and don't be offended

 

[Trip]

Your problems might be:

-Pressure leaks in the system
-Actuator diafragm punctuated and leaking pressure
-Actuator not working properly
-Manual boost controller -->IF I WERE YOU, I WILL BIN IT IMEDIATLY AND GET AN ELECTRONIC ONE!!!!!!!!
-Incorrect electronic setup

These are basicly the things that can go wrong.

Please take this an advice and don't be offended

- What might i have wrong in my Electronic setup to delay boost ?
- There is nothing wrong with the manual boost controller. I have an electronic one (blitz) wired but i do not trust it.
- I will pressure test the actuator and see at what PSI it opens. and if it leaks.

Everyone is mentioning this bloody pressure leaks but i am not sure what should i look for when i do the pressure test.. I am sure that no engine in the world is airtight and it will leak to a degree. My question is, should it hold let say 2bar of pressure for an Hour without dropping or should it drop slowly and still be OK ?

thank you

 

[watoga]

Was the leak evident visually and how much did it effect the boost delay ?

I had a leaking manifold gasket. Visually, no signs of damage were apparent. However, it did produce a flapping sound at idle, which was even audible inside the car. This also caused a significant boost delay - 1 bar wasn't achieved until around 5000 rpm.

My question is, should it hold let say 2bar of pressure for an Hour without dropping or should it drop slowly and still be OK?

I'd like to know the answer to this also! ;-)

Thanks and good luck,
Dave

 

[stumo]

Trip, i posted a reply earlier but it's gone....

Check to see if the boost controller works properly.....do you have it fitted the correct way round? Also check the actuator works properly too.

the boost controller shouldn't allow any pressure to get to the actuator until the pressure that it is set to.

example, if you have the controller set to 17psi, then until 17 is reached you shouldn't get ANY air coming out of the outlet that goes to the actuator. As soon as 17 is reached the ball bearing will come off it's seat and you will get air coming out of the outlet.

If you do get air coming out before the set pressure is reached then the controller isn't working correctly.

I wouldn't change it for an electrical one unless it was either one of the AMS units (either the 1000 or the 500) but you'd need a dual port actuator to properly use them.

Is there enough preload on the actuator rod? you should have approx half a hole of preload.

When we say there's a boost leak, pressurise the inlet side and see if there's leaks from pipes, joints, gaskets etc etc. You will always get the air leaking through the engine, past the rings so you can discount that.

 

[stumo]

Going back to the ign timing....

A mate was looking at a supercharged Honda engined Elise that had suddenly lost power......he found that the the timing was retarded by something like 5 degrees and they'd lost a huge amount of power, in the region of 70lbft and 70 hp!!!

SO, imagine that on a R where the engine has to be making power to get the turbo to start spinning sufficiently fast to start making boost, you retard the timing, power goes down and so will the ability to make boost....

 

[Trip]

I had a leaking manifold gasket. Visually, no signs of damage were apparent. However, it did produce a flapping sound at idle, which was even audible inside the car. This also caused a significant boost delay - 1 bar wasn't achieved until around 5000 rpm.

Good to know that such a small leak will upset the boost. I will check my manifold. thanks

 

[Trip]

Trip, i posted a reply earlier but it's gone....

Check to see if the boost controller works properly.....do you have it fitted the correct way round? Also check the actuator works properly too.

the boost controller shouldn't allow any pressure to get to the actuator until the pressure that it is set to.

example, if you have the controller set to 17psi, then until 17 is reached you shouldn't get ANY air coming out of the outlet that goes to the actuator. As soon as 17 is reached the ball bearing will come off it's seat and you will get air coming out of the outlet.

If you do get air coming out before the set pressure is reached then the controller isn't working correctly.

I wouldn't change it for an electrical one unless it was either one of the AMS units (either the 1000 or the 500) but you'd need a dual port actuator to properly use them.

Is there enough preload on the actuator rod? you should have approx half a hole of preload.

When we say there's a boost leak, pressurise the inlet side and see if there's leaks from pipes, joints, gaskets etc etc. You will always get the air leaking through the engine, past the rings so you can discount that.

I have much more then half a hole of preload on the actuator rod. if i remember correct it was slightly over the full diameter of the hole (diameter of the actuator rod hole). The spring was pulling hard and i just managed to pull the rod out to clamp it into place with my bare hands.

I will pressure test my MBC and see if it leaks air.

As for my timing, i'll get my timing lights out and check it.


Thank you once again.

 

[pulsarboby]

in answer to pm trip the very first thing i would check would be your ign timing, set that to 20 degrees base idle then take the car for a blast. a mere 2 degrees out will delay tubby and cause lag issues.

assuming thats all ok then dis-connect the vacuum from actuator and blank the pipe so tubbys running unlimited boost, take car out and just do one hard pull in it....and i mean just one in say second gear. if the turbo spools up quickly then come off boost immediately, then the chances are that you either have a dodgy boost controller or possibly a weak spring in actuator, you shouldnt really be running a 2871 on a bleed valve anyway tbh.

my guess is that its one of the above but i would take a real close look at that ign timing;-)

if neither the above make any difference then let us know

 

[Trip]

in answer to pm trip the very first thing i would check would be your ign timing, set that to 20 degrees base idle then take the car for a blast. a mere 2 degrees out will delay tubby and cause lag issues.

assuming thats all ok then dis-connect the vacuum from actuator and blank the pipe so tubbys running unlimited boost, take car out and just do one hard pull in it....and i mean just one in say second gear. if the turbo spools up quickly then come off boost immediately, then the chances are that you either have a dodgy boost controller or possibly a weak spring in actuator, you shouldnt really be running a 2871 on a bleed valve anyway tbh.

my guess is that its one of the above but i would take a real close look at that ign timing;-)

if neither the above make any difference then let us know

Thanks for the reply Bob

The timing is the first thing to check once i manage to get hold of the timing lights. I will do some runs with actuator disconnected and bypassing the boost controller and see what happens.

The one i am using is not a bleed valve, its a ball and spring type. 2 friends of mine are using this identical device with great success.

 

[pulsarboby]

Thanks for the reply Bob
I will do some runs with actuator disconnected and bypassing the boost controller and see what happens

not runs ev you only wanna be doing this once or twice max or youll blow the turbo or worse still your engine to pieces, you should see the difference immediately if thats the prob.
soon as the boost starts to really come in keep an eye on your boost gauge then lift off as its approaching around 1.4 bar

 

[Trip]

not runs ev you only wanna be doing this once or twice max or youll blow the turbo or worse still your engine to pieces, you should see the difference immediately if thats the prob.
soon as the boost starts to really come in keep an eye on your boost gauge then lift off as its approaching around 1.4 bar

Don't worry bob.. it was just a figure of speech. It's not difficult to figure out the after effects of running unlimited boost ;-)

 

[ZED_not_zee]

lol a friend of mine pulled his actuator line with his Mitsubishi eclipse TSI in the final round of the last race of the season,,, he won with a 10.89 pass. (drag strip) and crossed the lights with a blown motor... he one almost as much money as the rebuild cost TOTALLY worth it!