I can but agree that the wastegate made a big difference; in my case the OEM one was already imperfect (not u/s but not perfect either) - so a not totally fair comparison. But unquestionably better in the lower rev range. As I implied and you said, for anyone else looking at replacing their wastegate, look at a dual port design - *much* cheaper as well as being more modern, more effective technology.
930/964 turbo 3.3 vs 3.6?
- Thread starter Beebop
- Start date
I have bought a Tial and fitted it, but not used it yet.
How does a dual port benefit an engine ?
EDIT : I just googled it and it seems that the 930 has a dual port WG. The second port (the top part) is the part that normally vents to the atmosphere in the engine compartment ? I will have this connected to my EBC.
How does a dual port benefit an engine ?
EDIT : I just googled it and it seems that the 930 has a dual port WG. The second port (the top part) is the part that normally vents to the atmosphere in the engine compartment ? I will have this connected to my EBC.
Hi Scott.
I remember reading in 911 & Porsche World that the springs get tired in the 944T wastegates and there was a company that offered to shim them up to get back to normal performance. This obviously is much cheaper than replacing it.
If the 930 was watercooled we could get even more BHP [
]
I remember reading in 911 & Porsche World that the springs get tired in the 944T wastegates and there was a company that offered to shim them up to get back to normal performance. This obviously is much cheaper than replacing it.
If the 930 was watercooled we could get even more BHP [
]
sawood12
New member
Wastegate shimming is a common thing on 944T's and is a method of pre-loading a tired spring but is only a stay of execution. The fundamental design problem with a single port wastegate is that the wastegate valve is held shut by a spring. The spring will be rated to fully open the valve at the pre-determined pressure but as we all know a spring deflects when any force is applied meaning the valve will crack open long before the intended max boost pressure is achieved and the valve opens fully. Because a dual port design relys on two pressure signals on either side of a diaphram (manifold pressure vs. set intended max pressure) the valve will remain firmly closed until there is a pressure differential across the diaphram that opens the valve - therefore allowing the boost pressure to build more quickly and minimising lag.
Another problem I found with my wastegate is that the body of the wastegate is cast and includes a number of cooling fins. Upon removal of my wastegate I found that the housing had a dirty great big crack right the way along the valley between two cooling fins meaning even when my wastegate valve was closed I was still leaking exhaust pressure through the housing thereby increasing lag. Although I don't believe this is a very common problem it is not unheard of. I'm not sure if the 911 turbo wastegate housings are manufactured in a similar way and to a similar design but this might be another failure mechanism of the wastegate that it's worth being aware of. The Tial wastegate bodies are CNC machined from billet Aluminium Alloy so better, stronger material is used and the surface finishes achieved are much better than the OEM cast bodies thereby reducing/eliminating the risk of cracking. Unfortunately the dual port wastegate I bought was from a company that takes old OEM wastegates and modifies them retaining the original cast body, so for me the housing cracking problem is still a risk. If I were to do it all again I would have got a Tial.
Another problem I found with my wastegate is that the body of the wastegate is cast and includes a number of cooling fins. Upon removal of my wastegate I found that the housing had a dirty great big crack right the way along the valley between two cooling fins meaning even when my wastegate valve was closed I was still leaking exhaust pressure through the housing thereby increasing lag. Although I don't believe this is a very common problem it is not unheard of. I'm not sure if the 911 turbo wastegate housings are manufactured in a similar way and to a similar design but this might be another failure mechanism of the wastegate that it's worth being aware of. The Tial wastegate bodies are CNC machined from billet Aluminium Alloy so better, stronger material is used and the surface finishes achieved are much better than the OEM cast bodies thereby reducing/eliminating the risk of cracking. Unfortunately the dual port wastegate I bought was from a company that takes old OEM wastegates and modifies them retaining the original cast body, so for me the housing cracking problem is still a risk. If I were to do it all again I would have got a Tial.
Great info, thanks.
So this is why a EBC can improve build up of boost without overboosting ?
So this is why a EBC can improve build up of boost without overboosting ?
sawood12
New member
Tials are a simple replacement of the OEM unit, the only tricky thing is that since Tials are an aftermarket product for use on many different makes of cars the OEM support bracket does not fit onto them and I didn't like the idea of the weight of the wastegate being totally supported by the exhaust system which is why I went for a modified OEM product (before I knew about the casting cracking problem). However there are a couple of guys on the 944 forum who have fabricated support brackets for their Tials so if you know someone with the right equipment and skills you should be able to get something made. If you are using the wastegate in Dual Port mode you need to feed a 2nd boost feed to the second port that goes via some sort of boost control device. I've got a manual (mechanical) boost controller (£30) which is a simple valve that can be adjusted to limit the boost to a max level so it builds up along with the manifold pressure but is limited to a max value afterwhich the manifold pressure overcomes the set boost pressure and opens the wastegate.
Electronic Boost Controllers (EBC's) are really the best (and safest) way to go and give you effectively closed loop control of the boost. You can also use them to set boost profiles to customise the feel of the powercurve to something you want. There are other bells and whistles you can achieve with EBC's which vary from manufacture to manufacturer but since I havn't got one I can't really give you the detailed low down on what they can do. EBC are a bit more pricey and start from about £300 for one worth having and can go upto significantly more than that for some with more bells and whistles.
Don't forget you also have to consider fuelling - especially if you intend to increase the max boost pressure. Before I uprated my chips I got apparent overboost problems. This was due to the boost building so quickly due to the DPW and tricking my ECU into thinking the engine was overboosting and so triggering the overboost protect mechanism which effectively retards the ignition timing by 6 degrees. Under full accellaration this feels like a very violent and sudden engine braking effect - very scarry, potentially dangerous and damaging so not a situation you really want to be getting into. As soon as I upgraded my ECU chips this is no longer a problem as the chips have been programmed to work with a DPW. Obviously if you are increasing your boost levels you need to make sure the ECU can command the extra fuel to prevent the A/F ratio from leaning out and heating up. If you fuel your air properly I see no reason why you cannot significantly increase boost levels even on the air cooled cars as the combustion temps are governed by your A/F ratio - in fact you can overfuel to effectively cool the combustion temperatures if you are really pushing the boost pressures. On the 944 you can certainly safely go upto 1bar boost and even upto 1.2 bar boost with the standard fuel injectors and fuel pump. Any more than that and larger injectors and fuel pumps are needed to deliver the required fuel. To put that into perspective a 944 250turbo is potentially good for upto 320bhp at 1.2 bar boost.
Ultimately if you've got the motivation and deep enough pockets the sky's the limit! My aims are simply to update the performance of my car and with more modern chips improve (yes imrprove) fuel economy and emissions - i'd be happy with a mere 300bhp. There are others over on the 944 forum that are after out and out power (well over 400bhp) and they have developed some very clever and interesting bits of kit for their cars like electronic coil-over spark plug ignition systems which make the stock electro-mechanical distributor redundant and utilise state of the art aftermarket ECU's.
Electronic Boost Controllers (EBC's) are really the best (and safest) way to go and give you effectively closed loop control of the boost. You can also use them to set boost profiles to customise the feel of the powercurve to something you want. There are other bells and whistles you can achieve with EBC's which vary from manufacture to manufacturer but since I havn't got one I can't really give you the detailed low down on what they can do. EBC are a bit more pricey and start from about £300 for one worth having and can go upto significantly more than that for some with more bells and whistles.
Don't forget you also have to consider fuelling - especially if you intend to increase the max boost pressure. Before I uprated my chips I got apparent overboost problems. This was due to the boost building so quickly due to the DPW and tricking my ECU into thinking the engine was overboosting and so triggering the overboost protect mechanism which effectively retards the ignition timing by 6 degrees. Under full accellaration this feels like a very violent and sudden engine braking effect - very scarry, potentially dangerous and damaging so not a situation you really want to be getting into. As soon as I upgraded my ECU chips this is no longer a problem as the chips have been programmed to work with a DPW. Obviously if you are increasing your boost levels you need to make sure the ECU can command the extra fuel to prevent the A/F ratio from leaning out and heating up. If you fuel your air properly I see no reason why you cannot significantly increase boost levels even on the air cooled cars as the combustion temps are governed by your A/F ratio - in fact you can overfuel to effectively cool the combustion temperatures if you are really pushing the boost pressures. On the 944 you can certainly safely go upto 1bar boost and even upto 1.2 bar boost with the standard fuel injectors and fuel pump. Any more than that and larger injectors and fuel pumps are needed to deliver the required fuel. To put that into perspective a 944 250turbo is potentially good for upto 320bhp at 1.2 bar boost.
Ultimately if you've got the motivation and deep enough pockets the sky's the limit! My aims are simply to update the performance of my car and with more modern chips improve (yes imrprove) fuel economy and emissions - i'd be happy with a mere 300bhp. There are others over on the 944 forum that are after out and out power (well over 400bhp) and they have developed some very clever and interesting bits of kit for their cars like electronic coil-over spark plug ignition systems which make the stock electro-mechanical distributor redundant and utilise state of the art aftermarket ECU's.
Nathan,
From wikepedia.org:-
"A dual port wastegate adds a second port on the opposite side of the actuator. Air pressure allowed to enter this second port aids the spring to push harder in the direction of closing the wastegate. This is exactly the opposite of the first port. The ability to help the wastegate remain closed as boost pressure builds can be increased."
Cheers,
Beebop
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