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I picked up a tt-rs manifold on ebay for $68 shipped and the stock vw fuel rail fits and I am going to cut off the the stock fittings and add 6an in/out and add new tabs for the mounting.. I may weld a flange with the correct bolt pattern or modify this and add material and re drill. Not sure yet. I am going to make bellmoths and my own plenum.
Do people upgrade injectors? If so to what? What are the stock injectors flow rate? Ohms?
What are people's thoughts on keeping the low speed flaps? It can't makie much difference on a track only car. I can use a 12v solenoid for actuation and a rpm triggered output from the ecu.
Last edited by pyropete125; 07-22-2024 at 10:32 PM.
I picked up a tt-rs manifold on ebay for $68 shipped and the stock vw fuel rail fits and I am going to cut off the the stock fittings and add 6an in/out and add new tabs for the mounting.. I may weld a flange with the correct bolt pattern or modify this and add material and re drill. Not sure yet. I am going to make bellmoths and my own plenum.
Do people upgrade injectors? If so to what? What are the stock injectors flow rate? Ohms?
What are people's thoughts on keeping the low speed flaps? It can't makie much difference on a track only car. I can use a 12v solenoid for actuation and a rpm triggered output from the ecu.
@pyropete125 What sort of engine are you building? Normally aspirated or turbo, and what sort of breathing modifications? The size/flow rate of the injectors is contingent on the previous question. There is no reason in 2024 to run low-impedance or "low-Z" injectors, that was a way to enable ancient ECUs to control large fuel injectors. There is a plethora of modern high-impedance (~12-14 ohm) fuel injectors available with all sorts of nozzle configurations, consult with a fuel injector specialist. I like RC Engineering and Five-O Motorsports, there are others as well.
You mention "track only" car, so you answered your own question about the low speed flaps, should probably get rid of them if that's the case. These tend to clog up with carbon in the case of under-maintained DFI VW/Audi applications in my experience. Wouldn't be a problem in a port-injected application like yours, but no reason to keep them, either.
I have long considered the 07K swap, but don't have direct experience, so I don't know all the ins and outs, but what is the reason for the TTRS lower intake manifold? Does it have larger ports, and do these match up to the port sizes of your 07K cylinder head?
You should start with what your setup is and what your build plans/goals are to get better answers.
@pyropete125 What sort of engine are you building? Normally aspirated or turbo, and what sort of breathing modifications? The size/flow rate of the injectors is contingent on the previous question. There is no reason in 2024 to run low-impedance or "low-Z" injectors, that was a way to enable ancient ECUs to control large fuel injectors. There is a plethora of modern high-impedance (~12-14 ohm) fuel injectors available with all sorts of nozzle configurations, consult with a fuel injector specialist. I like RC Engineering and Five-O Motorsports, there are others as well.
You mention "track only" car, so you answered your own question about the low speed flaps, should probably get rid of them if that's the case. These tend to clog up with carbon in the case of under-maintained DFI VW/Audi applications in my experience. Wouldn't be a problem in a port-injected application like yours, but no reason to keep them, either.
I have long considered the 07K swap, but don't have direct experience, so I don't know all the ins and outs, but what is the reason for the TTRS lower intake manifold? Does it have larger ports, and do these match up to the port sizes of your 07K cylinder head?
You should start with what your setup is and what your build plans/goals are to get better answers.
Turbo track car, with a spa manifold, but not a max effort car. Nothing internal for now. I just want to be able to have it reliable and only worry about changing oil, checking fasteners and bleeding the brakes between events.
The tt-rs manifold ports line up perfectly, the mounting bolts do not. The only benefit was the cost and time saved not having to weld the runners and machine the injector bungs and fuel rail.
I have a budget in mind and I want to fab many of my own parts for this in my car. In the future our lemons car/team may get an NA 07k if we can keep the cost down and it seems worth it.
*most of the time* the low-speed flaps across car MFRs is an emissions aid rather than any kind of actual performance benefit.
you should be OK to delete them here.
As a former 951 owner who still considers it one of the best designed cars in its class for the time period and since, i might have a somewhat unique insight to this endeavor given that my current daily is a '19 TTRS i bought new with >120K now on the OD:
The i5s floating around VWAG are rather distinct from each other and not necessarily derived from one another. The lightweight, hollow-cranked, 25PSI monstrosity they have in the last model TTRS/RS3 is something out of the shed in which they incarcerate overly ambitious Porsche, Lambo, Audi, and VW engineers.
My sneaking suspicion is that the cam profile was a concession to the flat 6ers to avoid any more embarrassment than the 75k MSRP TTRS already brought to the Porsche brand and continues to inflict in modified guises at tracks past end of production.
The heavier older motors might be technically stronger under E85+ grade applications but their weight with all of the plumbing and driveline adaptations might upset the balance F->R and you'd need axles made of wolverine's bones.
Modern VW motors have top ends to support the torque delivery strategy of "flat as a (tall) board." Getting them to deliver a progressive power band without it looking like something out of a 1320 video may require cams and a lot of control logic.
400lbft from 1740 (or pick one of their default outputs - this is just the more extreme version) is a handful without TC or AWD even if running a wavetrac/torsen/etc in the rear. The 951 is rather brilliantly designed to take advantage of a broad but progressive power band to let the driver determine how much torque to apply instead of Audi's VDC/TC/etc and these modern motors are intended for throttle-by-wire input modulation.
The cooling strategy for these things tends to depend on those big front-end maws of the sportier models (and even then, could be better as proven by the benefits of a carbon fiber intake setup and large FMIC) - take a look at what's inside the TTRS' nose for a sense of the fun. They have coolers in the side louvres, FMIC+AC+radiator in the front, and air charge is handled along the entire width of the grille via flat plenum converging into a generous intake.
Cold-side turbos never really caught on, if anything their relative distance form the exhaust valves is reducing. Despite the ingenuity of the heat-retaining wrap-around exhaust of the 951 for the time, its still energy lost and its lost to the space of the engine compartment further complicating the cooling scenario.
The "i4" was really half of a v8 placing the whole thing into the bay at a slant which helped to lower the 944's center of gravity - keeping that concern in-mind seems relevant to the part about managing unholy torque numbers at the other side of the car since body roll doesn't do well for keeping it going where intended even if compensating with something like EDFC-A
All the sensible nay-saying aside - sounds like a boatload of fun if and when it comes together
As a former 951 owner who still considers it one of the best designed cars in its class for the time period and since, i might have a somewhat unique insight to this endeavor given that my current daily is a '19 TTRS i bought new with >120K now on the OD:
The i5s floating around VWAG are rather distinct from each other and not necessarily derived from one another. The lightweight, hollow-cranked, 25PSI monstrosity they have in the last model TTRS/RS3 is something out of the shed in which they incarcerate overly ambitious Porsche, Lambo, Audi, and VW engineers.
My sneaking suspicion is that the cam profile was a concession to the flat 6ers to avoid any more embarrassment than the 75k MSRP TTRS already brought to the Porsche brand and continues to inflict in modified guises at tracks past end of production.
The heavier older motors might be technically stronger under E85+ grade applications but their weight with all of the plumbing and driveline adaptations might upset the balance F->R and you'd need axles made of wolverine's bones.
Modern VW motors have top ends to support the torque delivery strategy of "flat as a (tall) board." Getting them to deliver a progressive power band without it looking like something out of a 1320 video may require cams and a lot of control logic.
400lbft from 1740 (or pick one of their default outputs - this is just the more extreme version) is a handful without TC or AWD even if running a wavetrac/torsen/etc in the rear. The 951 is rather brilliantly designed to take advantage of a broad but progressive power band to let the driver determine how much torque to apply instead of Audi's VDC/TC/etc and these modern motors are intended for throttle-by-wire input modulation.
The cooling strategy for these things tends to depend on those big front-end maws of the sportier models (and even then, could be better as proven by the benefits of a carbon fiber intake setup and large FMIC) - take a look at what's inside the TTRS' nose for a sense of the fun. They have coolers in the side louvres, FMIC+AC+radiator in the front, and air charge is handled along the entire width of the grille via flat plenum converging into a generous intake.
Cold-side turbos never really caught on, if anything their relative distance form the exhaust valves is reducing. Despite the ingenuity of the heat-retaining wrap-around exhaust of the 951 for the time, its still energy lost and its lost to the space of the engine compartment further complicating the cooling scenario.
The "i4" was really half of a v8 placing the whole thing into the bay at a slant which helped to lower the 944's center of gravity - keeping that concern in-mind seems relevant to the part about managing unholy torque numbers at the other side of the car since body roll doesn't do well for keeping it going where intended even if compensating with something like EDFC-A
All the sensible nay-saying aside - sounds like a boatload of fun if and when it comes together
@TurboSlipNot All salient points, and well said. I've been sitting on the sidelines and monitoring this thread since the beginning, would already have pulled the trigger long ago if it weren't for arcane California smog rules (another subject for another time).
However, the big takeaway for me is the 07K setup is more compact and lighter than the 944 engine, which is huge and heavy for what it is. Properly building a 400+ hp 951 engine that will last for track use is a tall order, and quite expensive. It can be done, but for myself I'd rather sink that money into something more unique. My 951 has over 180K miles on the original (and tired, over 10K track miles) bottom end, but have VEMS engine management and an Evergreen K27/8 hybrid turbo, probably close to 400 bhp and torque at the the crank, don't need much more than that, but staring down the barrel of an engine rebuild, and I'm also kind of tired of working in the cramped 951 engine bay.
07K swap would probably be easier to work on for the most part (be sure to replace all the rear-mounted timing chain components and drive before installation!). Plus the unique sound and modern cylinder head and port design, already has COP ignition, etc.
I understand your point about the modern VAG engines and their more complicated torque request-based engine management. For a 951 application, would probably run a cable throttle to simplify things, and controlling basic variable intake camshaft timing is doable with modern engine management. The Haltech setup sold by Boost Brothers garage is a popular and well-supported platform both in the US and abroad, so finding a dyno tuner should not be too difficult.
You also raise a good point about cooling. 951 has a smaller frontal area/apertures for cooling, but there is still room for a large radiator and engine oil cooler(s). My current setup is a second factory 951 oil cooler plumbed in series with the original, oil and coolant temps stay in check even during a 100 degrees F track session at Willow Springs (which I refuse to do anymore, in any case). A/C is removed, though, so no condenser in front of the stock radiator. There are a few aftermarket 951 radiator/oil cooler options that look good.
However, the 07K engine in 944 sits further back than the stock engine, so plenty of room for hot air to exit the heat exchangers compared to any VAG application (Audi loves to shove the engine right up against the radiator, whether longitudinal or transverse), so I don't think the relative lack of front grille area is much of an issue. There is room to do a V-mount intercooler/radiator setup with vented hood in higher-output applications if that is needed.
I know it would seem a waste to spend all the money, time, and effort to convert to 07K and not take full advantage of the power potential of the setup due to the limitations of the RWD 944 platform, but it's a unique and fun way to modernize the power plant, kinda sorta keep things in the VAG family, and it would sound way better than a 944 mill. IMHO, if course
@TurboSlipNot All salient points, and well said. I've been sitting on the sidelines and monitoring this thread since the beginning, would already have pulled the trigger long ago if it weren't for arcane California smog rules (another subject for another time).
However, the big takeaway for me is the 07K setup is more compact and lighter than the 944 engine, which is huge and heavy for what it is. Properly building a 400+ hp 951 engine that will last for track use is a tall order, and quite expensive. It can be done, but for myself I'd rather sink that money into something more unique. My 951 has over 180K miles on the original (and tired, over 10K track miles) bottom end, but have VEMS engine management and an Evergreen K27/8 hybrid turbo, probably close to 400 bhp and torque at the the crank, don't need much more than that, but staring down the barrel of an engine rebuild, and I'm also kind of tired of working in the cramped 951 engine bay.
07K swap would probably be easier to work on for the most part (be sure to replace all the rear-mounted timing chain components and drive before installation!). Plus the unique sound and modern cylinder head and port design, already has COP ignition, etc.
I understand your point about the modern VAG engines and their more complicated torque request-based engine management. For a 951 application, would probably run a cable throttle to simplify things, and controlling basic variable intake camshaft timing is doable with modern engine management. The Haltech setup sold by Boost Brothers garage is a popular and well-supported platform both in the US and abroad, so finding a dyno tuner should not be too difficult.
You also raise a good point about cooling. 951 has a smaller frontal area/apertures for cooling, but there is still room for a large radiator and engine oil cooler(s). My current setup is a second factory 951 oil cooler plumbed in series with the original, oil and coolant temps stay in check even during a 100 degrees F track session at Willow Springs (which I refuse to do anymore, in any case). A/C is removed, though, so no condenser in front of the stock radiator. There are a few aftermarket 951 radiator/oil cooler options that look good.
However, the 07K engine in 944 sits further back than the stock engine, so plenty of room for hot air to exit the heat exchangers compared to any VAG application (Audi loves to shove the engine right up against the radiator, whether longitudinal or transverse), so I don't think the relative lack of front grille area is much of an issue. There is room to do a V-mount intercooler/radiator setup with vented hood in higher-output applications if that is needed.
I know it would seem a waste to spend all the money, time, and effort to convert to 07K and not take full advantage of the power potential of the setup due to the limitations of the RWD 944 platform, but it's a unique and fun way to modernize the power plant, kinda sorta keep things in the VAG family, and it would sound way better than a 944 mill. IMHO, if course
Practical r&d is never a waste IMO - money is relative and just a means to whatever hopefully productive ends someone has. The geometric and weight advantages sound salient, potentially shaving seconds off lap times, and I can attest to the i5's durability in stock form with improved intake cooling/flow.
The cable throttle thing might end up not being the easier avenue but that depends on how you plan to manage the whole thing. Personally I'd look to go the other way - I know it's not purist, but like DCTs: it wins.
Re making this sort of power on a built motor - I have a 3.8 v6 putting well north of 1k to the deck and its been doing that since 2020 to include a bunch of race events. It all just depends on whether you want to use existing well established patterns or delve into the various engineering disciplines of purpose-built stuff.
2) a completely dressed 944 NA motor is 400lbs (incl manifolds, accessories, clutch/bellhousing). i imagine a 951 is in the ballpark of 50-100lbs more with the turbo and plumbing added. neither an iron or alum block 5-cyl is going to affect the weight balance that much and even if it did it's not actually that big a deal.
3) torque curves are primarily set by displacement, manifold tuning, and variable cam timing can smooth it out. if you locked the VVT and left displacement/manifolds alone you would have a more conventional torque line.
3.2) traction control/abs/etc can make a race driver go faster when part of a coherent package. but they are put on street cars because of safety regs to keep overconfident drivers out of the ditch. driving a 944/968 with 400lbft+ in the 1000rpm range is not really that much harder than a standard car, if you are expecting it all to be there. i've driven several V8 944s, and one 525+hp 6.2L 968 a bunch of times, and your throttle pedal modulation is all it takes.
3.3) a 951 has a radiator core not much larger than that of a MK1 Golf but they do just fine because they have excellent stock fans. from my observations (based on spending a LOT of time looking for alternate radiators for a 944 chassis) is that MFRs fit as much radiator area as they can into a chassis, but there are NOT hard and fast rules or really even rules of thumb for cross section vs HP/displacement. however there is cooling efficiency to be gained by making a radiator as large CSA as you can, but thinner, which is why so many cars have 16mm single cores rads. but there are work-arounds if you can spend the $$.
4) this is an interesting one but consider the stock 944 engine - it is slanted over because it needed to fit under a 924's hoodline. it actually sits more upright than it would if it were just half a V8 - the V8 bank angle vs vertical is 45 degrees, a 944 is about 30 degrees. they have huge thick heavy camshaft towers with a large, long iron camshaft in them all the way up top, with a 10lb thick cast aluminum intake manifold next to that. i don't know the real numbers but i suspect a 944 engine cG is higher than you might think.
For future reference, is it safe to say that the O7k (CBT/CBU) from the 08+ cars is the better motor to build because of the better cam chain setup and the fact that a TTRS/RS3 crankshaft will drop in?
Practical r&d is never a waste IMO - money is relative and just a means to whatever hopefully productive ends someone has. The geometric and weight advantages sound salient, potentially shaving seconds off lap times, and I can attest to the i5's durability in stock form with improved intake cooling/flow.
The cable throttle thing might end up not being the easier avenue but that depends on how you plan to manage the whole thing. Personally I'd look to go the other way - I know it's not purist, but like DCTs: it wins.
Re making this sort of power on a built motor - I have a 3.8 v6 putting well north of 1k to the deck and its been doing that since 2020 to include a bunch of race events. It all just depends on whether you want to use existing well established patterns or delve into the various engineering disciplines of purpose-built stuff.
Again, good points made, some of which lead to the discussion of why the 944 platform in the first place----well, we all like it, otherwise we wouldn't be discussing things on this forum. But, the 944 Turbo crowd has always been an interesting one. I have been reading this forum since high school in the late '90s-early 2000s, it used to be a weird and sometimes nasty place with all the sniping in and one-upmanship. I have always loved these cars as a "budget" alternative to various 911 derivatives, along with its style and practicality.
The 951 crowd has by and large been a "frugal" group If I am putting it kindly ("cheapskate" sometimes seems more appropriate ), so it has always been a difficult market for vendors and parts developers to cater to. There are several notable high-dollar builds, most of which have been documented on this forum, people who simply love the 944 platform enough to take it to higher levels. But, for every one of those, there are about 100 people who want their speed on the cheap.
Now in 2024, there seems to be a newer generation of 951 owners, those who have always admired the car from afar, and may even be coming from newer Porsche models. It will be interesting to see if any of them step up and make serious attempts to modernize the platform, especially given the recent popularity of high-end "resto-mod" versions of various classics. For a pure performance rear transaxle car, it might make more sense to start with a C5 or C6 Corvette, but I think I speak for a lot of us when I say I wouldn't be caught dead in one of those .
For future reference, is it safe to say that the O7k (CBT/CBU) from the 08+ cars is the better motor to build because of the better cam chain setup and the fact that a TTRS/RS3 crankshaft will drop in?
Yes the later motors are better revised timing chains.
I think all cranks can be swapped- early and late 07k and tt-rs cranks. Early motors can have forged cranks here and there identified by forging cast lines on the sides of the journals.
Vw 07k cranks 6 bolt flywheel- mostly cast and a few forged
Audi cranks 8 bolt forged.
Edit: the timing chain and components must be used for the crank being used (early crank = early timing chain assembly),, but can be used in early and late blocks.
Lots of info in this video. https://youtu.be/56SMBotUyJI?si=h8rNI_0BNo2UDBPB
Now to debate if the vw forged cranks are as strong and the audi forged....
Last edited by pyropete125; Yesterday at 03:11 PM.
07-08-2024, 07:41 PM
