Just looking at the MK2 engine cosworth YB t34 with greens etc usual 330 bhp...
I have an issue with the boost.
The car does normally boost at 26psi.
Today when i wwnt in it it was only boosting to 21 / 22 psi and seemed to be getting very hot.
I also have noticed that when the car was in neutral and you rev it the boost guage would normally go to zero but at best will go to -7.5 bar.
Any ideas i have seached for leaks but can't find anything.
Cheers
Tim
Anyone !
Properly mapped or good guess? What is the AFR doing? I would suspect burnt valves or timing slippage?
It's a Harvey Gibbs Map so should be OK....Not sure AFR's, but exhaust has always been sooty.
Car does not smoke, starts very well, idles perfect.
Would burnt valves not allow it to loose the vacuum ?
The timing are you thinking ignition or cam ?
I have checked ignition as the dizzy was marked and its not moved.
Mant thanks for your help, please keep ideas comming.
Last edited by Timsrs; 27-09-2015 at 21:35.
ignition timing wont of moved because it is not distributor controlled, dizzy just does cam phase and distributes the sparks.
if its running hotter my guess would be either a map sensor related fault so its under fueling, which will make it run hotter and possibly generate less boost as you wont have as much exhaust gas volume, or perhaps a fuel supply issue
Thanks Graham
I Have fitted a new MAP sensor ( lucky i had a genuine one spare )
Still same.
Im thinking boost leak, so getting a kit to test for leaks.
Engine actually runs lovely, so dont think anything internal.
You don't really need a kit to test for boost leak! I blocked off the turbo inlet using an aluminium car coffee cup pushed into the inlet boost hose, and then pressurised the system with an airline, using the boost gauge to see if it was leaking. Was amazed at everywhere you think is tight using mikalor clips that was leaking!
what duffer said,shove the air in one of the vacum pipes,put the engine on tdc no 1,then seal everything up
Thanks will give this a try...
Did you put the air in through the vac pipe ?
Suppose you need to open the throttle to get it round the system am i right ?
Regards
Originally Posted by Duffer
Yes, I used the pipe to the fuel pressure regulator to pressurise it. You can also watch the operation of the turbo actuator at the correct pressure providing you have the ignition on doing it this way.
No need to open the throttle, air pressure will equalise very easily around the system!
Just also make sure that you have the engine in a position where the valves are closed, or you will just be blowing air down the exhaust.
Sealed like this...
How do you close all valves at the same time , take the camshafts out ?
Just going back to the initial problem, the boost controller was saying over boost, and not actually hitting the desired boost.
Could there be a leak on the exhaust side somewhere that would cause this ???
Many thanks
Last edited by Timsrs; 29-09-2015 at 21:45.
As turbospud said, just get the engine in a position where either the inlet, or exhaust valves on each cylinder are closed.
Not possible, the boost controller will take its pressure reading from the same pressurised area within the inlet. Is your boost controller also your pressure gauge? If not maybe look to see if you have a leak in the vacuum pipe to the gauge?
If you have an external boost controller, and have been winding up the boost to try and get the boost to go higher on a different gauge, STOP! If thats the case, it's probably why its getting hot!
ive recently had a misfire under hard acceleration that took a while to find,it was leaking boost from the intercooler to the throttle body pipes, the engine is moving on the mounts and there wasnt enough flex on the intercooler pipework.there was also a few small leaks that showed up when testing
Hi
Yes I have both an external boot controller and a separate gauge.
I have not would it up to get more boost s this is counter acting the problem and I agree that once set should not be adjusted.
I have heard the chatter recently get louder.
This is why I am thinking exhaust manifold leak ( may be totally wrong though ).
I am hoping I will find some sort of leak.
Right...Did a boost leak test pressurised upto 2 bar and could only find a fairly small leak from around the bolt area on the turbo
Really , really lost now, i was to be honest expectiong a massive leak.
RIGHT....Update...
The car has always had some hesitation when feathering the throttle, and just asking opinions if what i have found could be the cause of my issues.
I have tested the TPS and have a reading of 5v closed, when i open throttle the reading lower gradually, then i open further and the reading shoots back up to 5v.
Would this make the car run rich.
When the throttle is wide open the reading fluctuates between 0.3v - 0.9v........
Would this give a lower boost ?
Would it also give a negative vacuum when being revved.
What ECU are you running Tim? L6 L8 P8?
L6.....
Cheers
Failing actuator, wind the arm up a couple of turns and see if the boost climbs
I clamped the small hose going to the actuator and it it was still the same.
The turbo has only done about 1000 miles and was fully rebuilt by CR Turbos...
Regards
RIGHT....Update...
The car has always had some hesitation when feathering the throttle, and just asking opinions if what i have found could be the cause of my issues.
I have tested the TPS and have a reading of 5v closed, when i open throttle the reading lower gradually, then i open further and the reading shoots back up to 5v.
Would this make the car run rich.
When the throttle is wide open the reading fluctuates between 0.3v - 0.9v........
Would this give a lower boost ?
Would it also give a negative vacuum when being revved.
Normally these scaling sensors work from a certain voltage and either get higher or lower they shouldn't shoot back up or down to the original possition i would change that and try it.
When I say failing I mean that the spring inside the actuator is going soft so won't hold/make boost
Thanks one arrived ( well a used from from Gary at RS CLASSICS 360 ), so goin to try that.
When in the escort there's very little room so had to take off throttle body.
Waiting for a new gasket before if fit.
I am certain that this is why my car was hesitating at light throttle.
Ok...Fitting the sensor and i have found some very conflicting info on how the PF01 is setup....
Mine (with the new sensor reads 4.42V throttle closed ( idle ) which gradually smootly drops to 0.41V ( throttle fully open......
Some people say that it should read 0V ( or their abouts ) throttle closed at idle, and as soon as the throttle is touched ( slightly open ) should jump to the 4.42V..then gradually lower to 0.41V
Which one is correct research is 50/50
Last edited by Timsrs; 11-10-2015 at 11:58.
The first option is correct it should never go to 0Volt
The PF01 has a step in it and should read open circuit when the throttle is fully closed, this is so that the ECU knows exactly when the throttle is completely shut in order to regulate the idle speed. Once cracked open, the voltage will drop and the Idle speed valve will be controlled fully open. This will cause your car to run badly at idle when incorrectly adjusted, but will not cause a boost issue. It can cause a hesitation as you mention because as the sensor wears (it is just a potentiometer after all) the tracks inside wear, and you will find points where the reading fluctuates, or drops out.
This is taken directly from the bigturbo website.
Quote "PF01 - this is a variable resistor but with a switch in series with the wiper so that when the throttle is closed the output goes open circuit. The idea behind this is that the closed position is clearly defined. The sensor must be set up so the slightest movement will close the switch and the voltage will change from 5v to 4.4v.(the voltage decreases to 0.35v when the throttle is fully open). The disadvantage is that the most likely fault is an open circuit due to wear or a wiring problem, which cannot be identified by the ecu and so will not flag up a fault. A faulty output could cut the fuel during normal driving causing misfires or an engine which won't rev. The setting up of the switch position is critical as the throttle does not have to open very far for the revs to rise and the ecu must realize that it is the throttle controlling the revs and not the idle speed control valve, the result may be surges or stalling. "
www.bigturbo.com under 'sensors'
If you change the TPS or any other sensor that has the potential to effect fueling/ign you should really get the fuel/ign map looked at again to make sure that it's still happy with the new sensors.
See...Both Duel & Duffer have oposite opinions
I can understand how both work but what's correct.
IIRC 2wd and 4wd differnt in teh way they work/are wired perhaps that expalins??See...Both Duel & Duffer have oposite opinions
I can understand how both work but what's correct.
You got a point here Graham.
Tim,
Have a look on www.bigturbo.co.uk - There is a section on there about sensors, how they work and how they are wired etc.
Worth a look,
Al
Cheers
i have seen that thread...
The wiring is correct, it's just the setting up that's of mixed oppinions.
I am going to run with 4.5V at closed and see how things go this weekend
Ta
2wd throttle Pots are black and 4x4 ones are Red and has Graham says work in the opposite ways. Having said that we have an Escort Cosworth on a P8 ECU and that's mapped for a black throttle Pot.
2wd ones pf01 are red and 4x4 ones pf09 are red or black. P8 wont work with a 2wd tps it has a switch in it you may have got that wrong the black on the p8 will be a pf09 trust me, if it is then it will run like shite and wont be black it would be red unless its a chinese copy .
Who dares winsPRO-ALLOY AGENT
Yes i have the PF01 ( RED )
Fitted today but still the same...
It runs like it's on 3 cylinders.
I have noticed that the ISCV operates when the engine is warm / hot....
Is this correct, t thought that when the engine is hot the ISCV should be fullt closed.
Ok i have the red PF01 and the wiring is all correct for the sensor.
The car when hot seems to be running on 3 cylinders.
i have noticed that when the engine is hot the ISCV is opening.
Should this not operate when enginbe is warm.
Still getting fuel smell around the pump but no leaks ??
Whats your thoughts on the ISCV operation when engine is hot ?
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