930 tuning
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Scott, do you have a link for those DPW's?
JBL930 - let me know what rolling road you use - you must be "close" to Bob Watson - I will use his road for the final tune, but happy to put the cars back to back on the same road when it is all done.....you seem to question the fuel delivery and power figures so only one way to find out!
Treecare930 - The dual port wastgate is one way to go - I use a greddy profec B boost controller - this feeds pressure on top of the diaphram so keeps the valve shut until it should open at the required boost. This also allows you to drop boost to "valet mode" when it is wet etc. Nathan seems to have covered everything else.
Treecare930 - The dual port wastgate is one way to go - I use a greddy profec B boost controller - this feeds pressure on top of the diaphram so keeps the valve shut until it should open at the required boost. This also allows you to drop boost to "valet mode" when it is wet etc. Nathan seems to have covered everything else.
Simon, I'm not questioning your power figures, certainly not with the boost your running, I might question your sanity 
, the dyno's I've used that give you an accurate print out of your boost and fuel curves across the rev range are the Dyno Dynamics cells at either G-Force or Weltmiester, I believe Weltmiester are not trading any more but G-Force are still in operation but trading under a different name, not sure what it is but someone might chime in.
I'm in Henley so yes Bob isn't far from me, he seams like a nice chap and obviously knows his stuff but I didn't feel too confident when my car was on his rollers, he only did one run and got wheel spin, charged me for a full session though, I didn't go away any wiser as to where my car was power wise really or where my fuel was, he just said "it's plenty rich enough", not exactly conclusive as far as I'm concerned!
When I find a solution to my WUR issues and a "modern" way to bring on boost enrichment and eliminate the pig rich mid range (most probably with the Brian Leask WUR and RPM solenoid) I'd be more than happy to team up and do a dyno run at G-Force, I'm not going to run your bonkers boost though so I'm sure you'll go home with the BHP medal! Actually lets get JamesE down on the same day and we can witness some real old school (with Motec) Porsche HP, he's probably at 650+ BHP with 1.2bar, that'll rattle your fillings
, the dyno's I've used that give you an accurate print out of your boost and fuel curves across the rev range are the Dyno Dynamics cells at either G-Force or Weltmiester, I believe Weltmiester are not trading any more but G-Force are still in operation but trading under a different name, not sure what it is but someone might chime in. I'm in Henley so yes Bob isn't far from me, he seams like a nice chap and obviously knows his stuff but I didn't feel too confident when my car was on his rollers, he only did one run and got wheel spin, charged me for a full session though, I didn't go away any wiser as to where my car was power wise really or where my fuel was, he just said "it's plenty rich enough", not exactly conclusive as far as I'm concerned!
When I find a solution to my WUR issues and a "modern" way to bring on boost enrichment and eliminate the pig rich mid range (most probably with the Brian Leask WUR and RPM solenoid) I'd be more than happy to team up and do a dyno run at G-Force, I'm not going to run your bonkers boost though so I'm sure you'll go home with the BHP medal! Actually lets get JamesE down on the same day and we can witness some real old school (with Motec) Porsche HP, he's probably at 650+ BHP with 1.2bar, that'll rattle your fillings
G Force is perfect - that is where I recorded the 475bhp figure.
I know what you mean re Bob Watsons rolling road. The road has smooth rollers so even at the 400bhp level we needed to let the tyres down and had too much wheelspin to get any meaningful figures. However, I personally think he knows his stuff and have been more than pleased with his work.
I'll be interested to hear how you get on with fueling - always more to learn as I regard myself as only a novice.
Sounds as though we need to arrange a Turbo rolling road day in the Spring. maybe we can get the Porsche Club interested?
I know what you mean re Bob Watsons rolling road. The road has smooth rollers so even at the 400bhp level we needed to let the tyres down and had too much wheelspin to get any meaningful figures. However, I personally think he knows his stuff and have been more than pleased with his work.
I'll be interested to hear how you get on with fueling - always more to learn as I regard myself as only a novice.
Sounds as though we need to arrange a Turbo rolling road day in the Spring. maybe we can get the Porsche Club interested?
Treecare, sorry for hijacking your thread but we aren't far off answering your questions anyway. If i was you i'd simply go with the gear from IA, it's a proven kit which works well together, get some pictures of your headers as this is one of the main areas to start and if you have already got them on your car you're in front, if i was putting a list together of necessary mods and i was putting them in order it would read like this
1) Check engines health, get a good independent to do a leak down test
2) Headers (if it turns out you've got standard ones then there are lots of choices, B&B, Haywood and Scott, GHL's, 9m etc)
3) Turbo (i'd stick the HFS on if you want to change your 7002, i've had a garrett unit on mine for the last couple of years which was meant to be the nuts but the HFS i have now is better, and it's a KKK which are supposed to be on our cars)
4) Intercooler
5) 1.0bar spring (or better still get an electronic boost controller, this will help with spool up and hold your desired pressure constant)
6) Cams (964 ones are great but also heard good things about SC Cams too)
You then need to have a look where you are fuel wise, there are a couple of things on the market to help get the fueling right and the most popular one at the moment is an adjustable WUR (warm up regulator), as standard it dumps fuel in once it detects boost which means you end up pig rich through the mid range and it eventually leans out at the top, (all standard old CIS turbos do this out of the showroom), what the adjustable one does to start with is it allows you to adjust cold start/idle pressure, warm pressure and on boost pressure which means you can get them all perfect instead of being stuck with whatever it is set at from the factory, then instead of it starting to dump fuel in when it detects boost you hook up a solenoid which triggers at a preset RPM level (say 4200rpm) so it only enriches when the engine actually needs it, this will really help with fuel economy and produce more power through the mid range, basically it's a good thing to have a nice flat AFR for a number of reasons.
After the above is done you're probably in the low 400bhp level, to go higher you really need to start strengthening stuff and porting, stronger rod bolts and head studs, possibly stronger con rods, flame-ringing the heads to run more boost, you could play around with the compression ratios, possibly go 3.4ltr, balance the crank and other rotating parts, strengthening the engine case by shuffle pinning, custom grind cams, the list is endless and for the above your fuel set up wouldn't be adequate so you would need to go EFI which then gets stupidly expensive.
Coming back down to earth, low 400bhp in a 930 is plenty, if you want it to go quicker then go lightweight, the seats weigh a ton for a start! You are probably fine with the turbo you have for now, you're getting a decent intercooler, fingers crossed you already have a set of decent headers on the car, get a boost controller, i'm not familiar with the duel port waste gate that has been mentioned but if it does the same job of holding the valve shut until you reach 1.0bar and holds 1bar up to the red line then great, you've got SC cams so to be honest your almost there, get it all fitted and up to G-Force and see where you are. Get some pics from under the car and get them posted
Simon, please can you post or e-mail me the dyno sheet showing your AFR's during the 475bhp run, i'd love to see it
1) Check engines health, get a good independent to do a leak down test
2) Headers (if it turns out you've got standard ones then there are lots of choices, B&B, Haywood and Scott, GHL's, 9m etc)
3) Turbo (i'd stick the HFS on if you want to change your 7002, i've had a garrett unit on mine for the last couple of years which was meant to be the nuts but the HFS i have now is better, and it's a KKK which are supposed to be on our cars)
4) Intercooler
5) 1.0bar spring (or better still get an electronic boost controller, this will help with spool up and hold your desired pressure constant)
6) Cams (964 ones are great but also heard good things about SC Cams too)
You then need to have a look where you are fuel wise, there are a couple of things on the market to help get the fueling right and the most popular one at the moment is an adjustable WUR (warm up regulator), as standard it dumps fuel in once it detects boost which means you end up pig rich through the mid range and it eventually leans out at the top, (all standard old CIS turbos do this out of the showroom), what the adjustable one does to start with is it allows you to adjust cold start/idle pressure, warm pressure and on boost pressure which means you can get them all perfect instead of being stuck with whatever it is set at from the factory, then instead of it starting to dump fuel in when it detects boost you hook up a solenoid which triggers at a preset RPM level (say 4200rpm) so it only enriches when the engine actually needs it, this will really help with fuel economy and produce more power through the mid range, basically it's a good thing to have a nice flat AFR for a number of reasons.
After the above is done you're probably in the low 400bhp level, to go higher you really need to start strengthening stuff and porting, stronger rod bolts and head studs, possibly stronger con rods, flame-ringing the heads to run more boost, you could play around with the compression ratios, possibly go 3.4ltr, balance the crank and other rotating parts, strengthening the engine case by shuffle pinning, custom grind cams, the list is endless and for the above your fuel set up wouldn't be adequate so you would need to go EFI which then gets stupidly expensive.
Coming back down to earth, low 400bhp in a 930 is plenty, if you want it to go quicker then go lightweight, the seats weigh a ton for a start! You are probably fine with the turbo you have for now, you're getting a decent intercooler, fingers crossed you already have a set of decent headers on the car, get a boost controller, i'm not familiar with the duel port waste gate that has been mentioned but if it does the same job of holding the valve shut until you reach 1.0bar and holds 1bar up to the red line then great, you've got SC cams so to be honest your almost there, get it all fitted and up to G-Force and see where you are. Get some pics from under the car and get them posted
Simon, please can you post or e-mail me the dyno sheet showing your AFR's during the 475bhp run, i'd love to see it
sawood12
New member
I only have links for 944 turbo DPW's. Linsay Racing in the states does a conversion of a stock one by removing the diaphram assembly off your stock wastetage and replacing it with one they manufacture so you are retaining the stock wastegate body so no installation issues (as with Tials). I've included the link below. They don't seem to do one for the 911 but its worth giving them a shout anyway.
http://www.lindseyracing.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=LR&Category_Code=944WASTEGATE
The only risk/disadvantage to this is that when I removed my original wastegate the cast body had a crack in it. I'm not sure if this is a weakness in the stock wastegate and if it is carried over to the 911 wastegate but its worth doing your research. Another option is to use a complete aftermarket wastegate. In the 944 turbo world Tial have a good reputation and seems to be the weapon of choice, though installation is more complicated but there are kits out there now. If I were to do it again i'd go with the Tial.
In terms of boost control, i'm using a mechanical valve that regulates the pressure to the second port of the wastegate i.e. the comparitor signal. These are cheap, robust, effective and i've had no problems at all, however they do bleed boost at high RPM. I've recently bought an Electronic Boost Controller (EBC) which is what Simon is referring to. These use an electrically actuated solenoid to replace the mechanical valve and is controlled by an electronic closed loop control system. These are able to actively hold boost through the rev range (as long as your turbo can flow enough air to maintain boost pressure) and though every gear and you can play allsorts of tricks with them. For example you can programme in different boost curves or even have different boost curves available at the touch of a button e.g. one for wet road (e.g. feeds boost in gently), dry road (e.g. feeds boost in quickly) and one for track (e.g. higher peak boost level to maximise power). These features are all fully programmable. All i've got to do now is install it!!
Obviously through all this you'll need to keep an eye on fuelling which is where your wideband o2 sensor will come in handy. It is usually the case in the 944 world that you will have to increase your fuel pressure and/or install larger injectors to ensure safe and correct fuelling.
Since installing my DPW i've never looked back and i'm sure when the EBC goes in it'll open up a whole other world. I've recently dynoed my car at 275bhp (meagre compared to your cars I know) but this is up from 220bhp and i'm still running modest boost pressure and therefore not compromising reliability and engine longevity. My boost builds progressively from just under 2krpm and peaks at about 3300 rpm but immediately starts to tail off. With my EBC I should be able to hold peak boost pressure for 1k to 1.5k before my turbo starts to run out of puff, which should get me knocking on the door of 300bhp at current boost pressure. After that i'm looking at a larger turbo and a MAF and should easily be able to get 350bhp, again at my current boost pressure. At that i'll call it a day as to get much beyond that i'm looking at increasing boost pressure and therefore a costly engine rebuild. I think that'll do me though!
The Tial I have is dual port and so is the stock 930 wastegate. The 944turbo stock wastegate wasn't.
Is knock a problem as you increase boost on these cars ?
Big problem in the impreza (but not the evo, strange). Some people swear by (or at) a knock indicator to give an on the road indication of problems.
Dump valves are a mysterious device, remember they are there to prevent compressor stall/surge not to reduce lag.
Big problem in the impreza (but not the evo, strange). Some people swear by (or at) a knock indicator to give an on the road indication of problems.
Dump valves are a mysterious device, remember they are there to prevent compressor stall/surge not to reduce lag.
sawood12
New member
Knock can be a problem at high boost pressures and is one of the things you need to look out for. I suspect Evo's and Impreza's run higher boost pressures than our Porsches which is why they get such good power out of a small capacity engine (it's not rocket science afterall). The stock 944 boost pressure is about 0.75 bar boost and I believe the 930 stock boost pressure will be around the same. Some people in the 944 world are running in excess of 1.2 bar boost pressure with stock ECU's, with re-mapped chips of course, on 97+ RON fuel and knock is not a big problem - espeicially if you ensure your fuel system is able to deliver the right amount of fuel by increasing the fuel pressure and/or installing larger higher flowing injectors. Also 944's and other Porsche models of that era have Knock computers and knock sensors so you do have some protection.
If your 930 wastegate is a dual port it should make tweaking boost pressure's a bit easier. However i'm flummoxed to imagine how you'd set about increasing the delivery of your mechanical fuel injection system! Ultimately you are not going to achieve large power increases without increasing your boost pressure. Well not without rediculously expensive engine rebuilds with custom made internals.
If your 930 wastegate is a dual port it should make tweaking boost pressure's a bit easier. However i'm flummoxed to imagine how you'd set about increasing the delivery of your mechanical fuel injection system! Ultimately you are not going to achieve large power increases without increasing your boost pressure. Well not without rediculously expensive engine rebuilds with custom made internals.
The 930 has no knock sensing equipment. The injection is K-jetronic or CIS. No computers here...
As for extra fuel, I have a fuel head that has been cnc'd larger to flow more fuel. To correct fuelling at different loads a chap in the USA mods the Warm Up Regulator (control pressure regulator) to make them adjustable. He also sells a rpm sensing switch which can block boost pressure going to the WUR (therefore preventing too rich a mixture) until a preset rpm is reached. Mostly there is too much fuel when the turbo first comes in at say 3k rpm until say 4k rpm. Without the switch above 5k rpm tends to be too lean and can melt the engine.
Jonathan, JBL930 has just got a new Digital Warm Up Regulator (DWUR) this is adjusted using software that runs on a PC. It should work but nobody has actually really tested one yet.
CIS / K-jet cannot use dump valves. We use recirculation valves. Bailey or Forge are good replacement recirc valves for the plastic Bosch valves that are used on the '91 on 911 turbo's.
My 930
1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.
As for extra fuel, I have a fuel head that has been cnc'd larger to flow more fuel. To correct fuelling at different loads a chap in the USA mods the Warm Up Regulator (control pressure regulator) to make them adjustable. He also sells a rpm sensing switch which can block boost pressure going to the WUR (therefore preventing too rich a mixture) until a preset rpm is reached. Mostly there is too much fuel when the turbo first comes in at say 3k rpm until say 4k rpm. Without the switch above 5k rpm tends to be too lean and can melt the engine.
Jonathan, JBL930 has just got a new Digital Warm Up Regulator (DWUR) this is adjusted using software that runs on a PC. It should work but nobody has actually really tested one yet.
CIS / K-jet cannot use dump valves. We use recirculation valves. Bailey or Forge are good replacement recirc valves for the plastic Bosch valves that are used on the '91 on 911 turbo's.
My 930
1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.
Exactly, thats why I asked.
With no knock protection built into the car, increasing boost might lead to knock and damage your engine without you knowing.
Sorry ,a terminology conflict - a recirc is a dump valve in many circles , just not a VTA dump valve. As you can imagine, in the impreza world many people completly misunderstand the function of the dump valve (or recirc if you like) and think its there to allow the compressor to maintain its speed by maintaining flow (which is daft as maintaining flow, takes energy from the momentum in the rotating mass and therfore actually slows the compressor)
sawood12
New member
I thought the dump valves of either type was to vent manifold pressure to prevent the pressure from shockwaving back down the manifold the wrong way and stopping your turbo from freewheeling and causing damage to your compressor as soon as you dump the clutch for a gear change and the boost pressure suddenly falls away? Also there is a school of thought that says a recirc valve that dumps the air into the intake of the turbo compressor actually helps the turbo to maintain RPM's in between changes thereby speeding up the pick-up of the turbo once you get back on the throttle. This has been hottly contested though and no-one in either camp seems to be able to produce any convincing proof either way.
Also the other problem with VTA dump valves is the noise they make. It may be OK on a beaten up Scooby when the driver is a Burberry cap donned 17yrs old, with a baby-soft goatee that flutters in the wind, because they already look like prats, but on a half decent car it is just wrong in every possible way!
The reason why some cars cannot use/should not use a VTA dump valve is because the air measurement device (MAF or AFM) has already measured the air coming into the intake and metered fuel accordinly. If you then vent some of that air you will be running too rich.
Do these high powered 930's run aftermarket ECU's then? Without being able to increase boost pressure how do you get significant power increases?
Also the other problem with VTA dump valves is the noise they make. It may be OK on a beaten up Scooby when the driver is a Burberry cap donned 17yrs old, with a baby-soft goatee that flutters in the wind, because they already look like prats, but on a half decent car it is just wrong in every possible way!
The reason why some cars cannot use/should not use a VTA dump valve is because the air measurement device (MAF or AFM) has already measured the air coming into the intake and metered fuel accordinly. If you then vent some of that air you will be running too rich.
Do these high powered 930's run aftermarket ECU's then? Without being able to increase boost pressure how do you get significant power increases?
A dump valve prevents the compressor from entering the stall/surge cycle.
When the flow falls below a certain point dependant on speed, the compressor stalls and discharge pressure falls to zero, this allows flow reversal, and also allows the compressor to leave the stall condition. The compressor then re-establishes flow and pressure into the plenum, reaches stall again and the cycle repeates itself. This repeated stall/surge cycle results in rapidly ocillating foward and reverse flow & pressure that can damage the compressor.
However, think of the compressor as a pump. Its doing more work when moving a mass of air, therfore when the dump valve is open, its doing more work moving a mass of air around. It takes this energy from the momentum of the rotating assembly, therfore it slows down quicker.
Some competition cars do not have dump valves and allow the turbo to enter the surge cycle (think of the sound the Audi sport quattro used to make, not the whooosing sound loved by subaru drivers, but a cyclic 'squeaking' sound of stall/surge).
When the flow falls below a certain point dependant on speed, the compressor stalls and discharge pressure falls to zero, this allows flow reversal, and also allows the compressor to leave the stall condition. The compressor then re-establishes flow and pressure into the plenum, reaches stall again and the cycle repeates itself. This repeated stall/surge cycle results in rapidly ocillating foward and reverse flow & pressure that can damage the compressor.
However, think of the compressor as a pump. Its doing more work when moving a mass of air, therfore when the dump valve is open, its doing more work moving a mass of air around. It takes this energy from the momentum of the rotating assembly, therfore it slows down quicker.
Some competition cars do not have dump valves and allow the turbo to enter the surge cycle (think of the sound the Audi sport quattro used to make, not the whooosing sound loved by subaru drivers, but a cyclic 'squeaking' sound of stall/surge).
The stock 930 boosts to 0.7bar.
You can boost a 930 to 1bar if you make the following improvements.
The stock K26 turbo is an old design, the newer K27 is more efficient, it makes less heat at the same flow. Therefore pre IC temps are lower than with the stock turbo.
The stock IC is not very efficient either. A later IC, whether a later stock 964t, Andial, Garretson, B&B, Kokeln (which is what I have) or a custom made IC is used the intake temps will be lower to the engine.
Many people have gone EFI in the USA, infact most have gone with a full engine management system controlling both spark and fuel.
However, I don't ever see me doing it to be honest due to the cost/trouble.
You can boost a 930 to 1bar if you make the following improvements.
The stock K26 turbo is an old design, the newer K27 is more efficient, it makes less heat at the same flow. Therefore pre IC temps are lower than with the stock turbo.
The stock IC is not very efficient either. A later IC, whether a later stock 964t, Andial, Garretson, B&B, Kokeln (which is what I have) or a custom made IC is used the intake temps will be lower to the engine.
Many people have gone EFI in the USA, infact most have gone with a full engine management system controlling both spark and fuel.
However, I don't ever see me doing it to be honest due to the cost/trouble.
Treecare, think hard before making any mods to your engine. Its a slippery slope - believe me, I know!!
You say you are using 3.2 Carrera heads. These are cast from a different material to the genuine turbo head. Porsche used a material called RR350 for the turbo heads because they knew the heads would see much higher temperatures. RR350, as the name implies, is an alloy "invented" by Rolls Royce for the last of the air cooled aircraft engines just pre world war 2. It maintains pretty good mechanical properties up to 350 centigrade and only some new VERY expensive silver loaded alloys beat it today - and really not by much. This alloy, when correctly heat treated, is the best you can sensibly use on a Porsche including all the wrought alloys now on the market. The standard 3.2 heads will go soft much quicker than the RR350 ones and you will risk losing clamping force between the head and the barrel.
More boost will compound the issues with the turbo. It will give more power but unfortunately this comes with more heat and more problems! The heads may go soft (see above), and the barrels can go out of round. Unless you have the fuelling/ignition spot on you can suffer detonation and this can split the barrrel due to the very high and fast increase in cylinder pressure caused by the expanding gas and the reducing volume!
There are lots of specialists that can "help" you but as someone else said choose them carefully otherwise you may end up spending a lot more money than you intended to!
I dont want to put you off because a well modified turbo is something else. They are powerful, reliable and produce thrills like no other. Just try and make sure you get it right first time!
Good luck,
Richard.
You say you are using 3.2 Carrera heads. These are cast from a different material to the genuine turbo head. Porsche used a material called RR350 for the turbo heads because they knew the heads would see much higher temperatures. RR350, as the name implies, is an alloy "invented" by Rolls Royce for the last of the air cooled aircraft engines just pre world war 2. It maintains pretty good mechanical properties up to 350 centigrade and only some new VERY expensive silver loaded alloys beat it today - and really not by much. This alloy, when correctly heat treated, is the best you can sensibly use on a Porsche including all the wrought alloys now on the market. The standard 3.2 heads will go soft much quicker than the RR350 ones and you will risk losing clamping force between the head and the barrel.
More boost will compound the issues with the turbo. It will give more power but unfortunately this comes with more heat and more problems! The heads may go soft (see above), and the barrels can go out of round. Unless you have the fuelling/ignition spot on you can suffer detonation and this can split the barrrel due to the very high and fast increase in cylinder pressure caused by the expanding gas and the reducing volume!
There are lots of specialists that can "help" you but as someone else said choose them carefully otherwise you may end up spending a lot more money than you intended to!
I dont want to put you off because a well modified turbo is something else. They are powerful, reliable and produce thrills like no other. Just try and make sure you get it right first time!
Good luck,
Richard.
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