Loss of boost
- Thread starter PSH
- Start date
PSH
PCGB Member
Hi guys
Well, I've spent some time today reading what's what in wastegate sizing and also watching my son take a look at the turbo. We are 99% happy to say it's not the turbo, with the intake pipe removed we could see/feel the impellor which still looks/feels as good as it did when new/rebuilt. Taking this and the fact that there were no other symptoms other than total loss of boost into account, we are thinking of a stuck open wastegate. When I say no other symptoms, I mean no smoke, no strange sound, car running as normal minus the boost since. The 1% is there just in case the impellor shaft has snapped but we think that's a very slim possibility but can't rule it out without removing the hot housing pipe which isn't going to happen any time soon.
Having made that decision it's now a question of what size WG to fit, now to date I had only read the stuff found on forums such as Rennlist etc. Today I dug a little further into this and as Paul has pointed out the bigger sizes are more for lower boost levels. My engine runs at a much higher boost, regularly at 1.5Bar, and has recorded 1.7 Bar with a large turbo, therefore the 38mm may be more suitable. Further reading showed up examples of 1000bhp street cars using 40mm WG's although to counter that some articles say the Tial 38mm is for power up to IIRC 580bhp. I also read into the spring rating and may go higher than the recommended 1/2 the boost figure.. I left a message for Tom at Augment to give me a call Monday so I can check my ideas with him.
To summarise, I'll probably take the chance and buy a new Tial, I honestly don't think it can be anything else with the total boost loss.
I'll keep you all up to date with what my final decision is once the WG has been selected/ordered.
Pete
Oh, in answer to Paul's question, yes the LR DPW was rebuilt by myself before the car was put back on the road.
Well, I've spent some time today reading what's what in wastegate sizing and also watching my son take a look at the turbo. We are 99% happy to say it's not the turbo, with the intake pipe removed we could see/feel the impellor which still looks/feels as good as it did when new/rebuilt. Taking this and the fact that there were no other symptoms other than total loss of boost into account, we are thinking of a stuck open wastegate. When I say no other symptoms, I mean no smoke, no strange sound, car running as normal minus the boost since. The 1% is there just in case the impellor shaft has snapped but we think that's a very slim possibility but can't rule it out without removing the hot housing pipe which isn't going to happen any time soon.
Having made that decision it's now a question of what size WG to fit, now to date I had only read the stuff found on forums such as Rennlist etc. Today I dug a little further into this and as Paul has pointed out the bigger sizes are more for lower boost levels. My engine runs at a much higher boost, regularly at 1.5Bar, and has recorded 1.7 Bar with a large turbo, therefore the 38mm may be more suitable. Further reading showed up examples of 1000bhp street cars using 40mm WG's although to counter that some articles say the Tial 38mm is for power up to IIRC 580bhp. I also read into the spring rating and may go higher than the recommended 1/2 the boost figure.. I left a message for Tom at Augment to give me a call Monday so I can check my ideas with him.
To summarise, I'll probably take the chance and buy a new Tial, I honestly don't think it can be anything else with the total boost loss.
I'll keep you all up to date with what my final decision is once the WG has been selected/ordered.
Pete
Oh, in answer to Paul's question, yes the LR DPW was rebuilt by myself before the car was put back on the road.
PSH
PCGB Member
If only life was that easy...blade7 said:
The car will need to be on a ramp and will need my sons to help, trying to get time on Richard's ramp is nye impossible and I'll probably only have a chance where it's a case of fitting a new part and them off. Taking the old one off to investigate and then fix may be pushing my luck. Plus is it can be fixed how long will it last before needing addressing again?
Best option is to rip out old and replace with new, even that may be pushing my luck with my son, he's a busy lad.
Pete
PSH
PCGB Member
Rebuilding the LR is a non starter . I recall when rebuilding it last time that there was a number of large cracks across the valve seat. I lapped the valve in as best I could but it became clear that the cracks were very derp, perhaps through the entire depth of the hardened seat, this probably means that the wastegate has always been bleeding a little boost. IIRC there was about 3 cracks more or less equaldistant around the seat. Thinking about this now, I wonder if one or more broken off sections of the sest have jammed the valve open? This is begining to make a lot of sense to my amatuer engineers mind.blade7 said:
Money isn't an issue, I just need to make a decision as to which size valve?
Hopefully Tom will return my call tomorrow and I can discuss this with him. Having now read into wastegates a lot over the last few days, the Tial is a superior design.
Pete
It’s 8 relatively easily accessible bolts - by the time you’ve made the brews and got the biscuits I imagine he’d have the wastegate almost removed.
As for WG sizing - I really think you’re overthinking it, if you remove the LR WG and it’s repairable then do that and refit. How many times do we tell people not to throw new parts at a problem "just because”? Of course, If you fancy treating yourself to a new WG as you’re indulging your hobby then go for it and no need to justify it.
As for WG sizing - I really think you’re overthinking it, if you remove the LR WG and it’s repairable then do that and refit. How many times do we tell people not to throw new parts at a problem "just because”? Of course, If you fancy treating yourself to a new WG as you’re indulging your hobby then go for it and no need to justify it.
Diver944
Active member
Best test for a wastegate that is stuck open is:
1. Start with a completely cold car
2. Start engine and let it idle
3. Lie on floor and alternately feel the exhaust then the wastegate exit pipe
4. If the exit pipe heats up at the same rate as the exhaust, the valve is stuck open and allowing hot gas to escape through it.
1. Start with a completely cold car
2. Start engine and let it idle
3. Lie on floor and alternately feel the exhaust then the wastegate exit pipe
4. If the exit pipe heats up at the same rate as the exhaust, the valve is stuck open and allowing hot gas to escape through it.
PSH
PCGB Member
blade7 said:
Everything can be fixed, IIRC I bought a new valve seat at the time but didn't fit it as it would have been a fair bit of extra work, plus I didn't have the tooling to machine it. I will keep it as a keepsake... I feel like a change anyway, the Tial will be interesting to compare, it will be fitted with a 1 BAR spring, I'll increase that if the response to the throttle is less than before. As stated in the past, it behaved more like an N/A low down than a turbo.
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