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Intercooling a Force Fed 968 - flash - 04-17-2011

correct



just for reference, 98 there is 93 here

Intercooling a Force Fed 968 - FraMac - 04-17-2011

thanks Flash for adding clarity.

Intercooling a Force Fed 968 - flash - 04-17-2011

no worries - i just didn't want anybody here thinking they needed to run super duper race gas to run your setup

Intercooling a Force Fed 968 - jfrahm - 04-17-2011

[quote name='flash' timestamp='1303050423' post='108552']

i have to ask the obvious question:



getting one of these right is more than just performance - if yours is the test mule, and even it does not run right (as defined by belt slip, which is NOT acceptable in any design), have you or anybody tried to get the vendor to correct this at his expense? i mean, if something doesn't work, the vendor should fix it or take it back - it seems to me that this would be the first stop - establish a baseline and then move on to more power - i keep hearing the vendor say that the system works, but if even the test mule didn't work right as delivered, i wonder which car does?



getting rid of the knurled pulley is a good first step - that will only add belt wear, not resolve it - adding wrap will help, either by larger pulleys, or adding more pulleys in strategically placed spots



this still won't resolve the poor fan issue, or the detonation issues which will result from running without tuning, or the supercharger heat issues, but at least you'll get to find out about those once it can actually run up there



lol - on the other hand, belt slip might keep you out of trouble, since it probably can't go high enough long enough to blow itself up

[/quote]



I do not think taking up the issue of the quality of the kit in this modding thread is appropriate, maybe you should start a supercharger comparison thread and we can discuss the shortcomings there? At any rate...



Lots of questions, but not a lot of context. Belt slip is a reality for belt drive systems. Belt drives slip. How much is too much? As I said before and on the other forum, it was manageable in my case. It's a performance add-on and in my experience those are rarely without issues or without need of tweaks so I do not know what is expected. Improving the kit is kinda fun for me so I'm happy to work on it in my spare time, plus improvements from Carl are not going to drive the blower faster and I am curious to see if I can do that as well.



I do not know how many kits have been sold and what percent of those buyers are happy or at least content. I dimly recall when I asked Carl about the number sold back in 2009 he said about 10.



I do not know if the knurled pulley works or not, I have not tried it. He sent me one, and it feels like it grips better than the stocker. clearly the belt slip issue is something Carl is addressing at his own expense as he is sending these out to his customers. I think the D1R kit has had some updates to it as well so neither were perfect from the get-go.



Again I was hitting 6-7 psi and hauling butt with the system as delivered and I could live with it the way it was and replace the belt when needed, but what I am doing now is more interesting and more fun.



I have not had any tuning issues or audible detonation (which I am quite familiar with.)



I have not had a problem with the radiator fan, it is not an impressive part but it seems to work.



This does not seem to have anything to do with intercooling so maybe these posts should be moved to the appropriate thread.



Cheers,

-Joel.

Intercooling a Force Fed 968 - flash - 04-17-2011

i just asked a question regarding solution attempts - it seems that should be asked prior to reworking the kit - did that not get done, or was it done and refused?



belt slip is not a reality or to be expected - it is unacceptable at any rpm the engine can generate - no belt should every slip - whether or not you choose to live with has nothing to do with the fact that it should not exist



yes, the D1R kit had one change made to align the belt a bit better, and i sent all of the parts out free to everyone, immediately upon discovery of the problem (which only showed itself on a couple of cars to begin with) but was not perfect, therefore i sent out the new parts - i immediately asked everyone to stop driving until the new parts were installed - with now well over 50k miles across the board on these kits, not one of them has belt slip



i'd love to know where the other 928 kits are - so far, not one of the installed kits has been shown to operate properly - as far as i know there are about 6, including yours



if you have not noticed the detonation, it is only because you can't hear it - it's there, and if you hooked up a tool, you would see the knock sensors going off - how much of a problem that is, depends on a lot of factors - the best case scenario is that the knock sensors are triggering, and the timing is being pulled back - that reduces the potential power, but if they can pull back enough timing, it will keep you out of trouble - the problem is the mixture - no matter how much fuel the rising rate regulator adds, the ECU will pull it right back out in less than one half second and return it to stoich at anything other than WOT - any boost on part throttle will not have enough fuel, and will ultimately cause damage - check it for yourself with an A/F meter - you won't be happy



all that being said, you are right that this is not directly related to intercooling, however my entire point was that i do not think that intercooling is needed nor desired at this boost level, and that if the other issues were resolved, that would very likely show itself - i was also making the point that these issues need to be resolved before intercooling - you need a solid baseline first when doing anything like this



so, it is related and appropriate though i did not want to get into any comparisons here - i merely wanted to point out the things that need to be addressed - i had to do it when i developed mine - it now appears that somebody needs to do it to complete the development of that kit

Intercooling a Force Fed 968 - craigawoodman - 04-17-2011

The main point of the post was to look at what you could do in terms of intercooling to potentially increase Horsepower and prevent engine damage.



When purchasing the 928 kit - I was very concerned that using the stock ECU maps was nowhere near good enough. If you are going to make bigger HP, you need to tune for it. Even a modern car will flash the ECU when boost pressure is raised, so it is not as simple as adding boost to a N/A car and letting the computer work it out. Hence why I went for an aftermarket engine management system.



In terms of pulleys, I am running the standard pulley that has been machined to accept a multi-vee belt. This should not be too hard to machine, if you are using tool steel, simply grind the cutting tool to the profile and cut the v-groove (this is how we used to do it 20 plus years ago when I was a machinist). Being aluminium, it should not be too hard to machine the drive pulley on a lathe.



Given what the people tuning my car have told me (and it has been on the dyno for over a full day now), the system cannot supply enough fuel at full throttle and high rpm. This could be due to the increased air flow from the multi-vee belt stopping slippage (but there is still some - but the belt probably needs re-tightening). I was told that the system was providing 4.5psi boost, but this is through an intercooler and also running the RSBarn high flow exhaust and on a brand new engine - so it should flow better.



The tuners also have stated that the rising rate fuel regulator cannot drop fuel quick enough when backing off - so overfuelling. This is why it needs to be removed.



I have to agree with Flash, in that if all of these problems exist with the standard kit (needs bigger injectors, overfuels when backing off, etc) - it is a recipe for disaster waiting to happen. I cannot afford to grenade a fully rebuild engine (although getting the tuning done is roughly half the cost of another rebuild). Hopefully when I am finished, I will have what the kit should have come close to delivering from the vendor - reliable, well tuned and fully sorted power. It will have cost me in excess of $10k on top of the kit to achieve this (excluding the engine rebuild). For what this project has cost, I could have purchased another 968.



It is Monday morning and I am scared to call the mechanic to see where the car got to over the weekend and whether or not it will be finished this week. I am also nervous to be putting it straight from the workshop to the track, so I have some soul searching to do. I am meant to be 1,650km away for scrutineering on Thursday. I then have another 3,500km to drive/tow after finishing the event.



As per previous posts, this build has taken over three months (car went to the mechanic on 10th January 2011).

Intercooling a Force Fed 968 - craigawoodman - 04-18-2011

Got a phone call from my mechanic. The car is tuned, just need some fine tuning of the idle and the bonnet to be modified. Interesting that the power made on the dyno was 290hp at the rear wheels - which is what the kit promised and around 330Nm of torque. I will post the dyno graphs once I get them. The biggest issue is that the kit will limit boost to around the 4.5psi mark through the blow-off valve and that with standard compression of 11:1, it causes pre-ignition. My mechanic's comment was that if you de-compress the engine, you will be able to advance the ignition more and run more boost. This will require a modification to the current relief valve arrangement. If you speed up the supercharger - you will make more boost down low, but it will still limit boost at higher rpm. If you don't then engine life is going to be an issue.



So going forward, the head will have to come off again and a thicker widefire gasket installed and another round of tuning performed. Indicatively, he believes that there is another 50 to 80hp available if these mods are done.



So if you are running the kit with a standard ingnition map and the originally supplied injectors - then based on what we have seen, you will have a problem.

Intercooling a Force Fed 968 - flash - 04-18-2011

the intercooler is probably costing you anywhere between 1 and 2lbs, so that boost level will produce those numbers - you may have cooler intake temps though, so it may be safer than without it - i would try it both ways and test intake temps - you might be surprised - with many intercoolers, on a low boost setup, the intake temps actually RISE due to restriction



as for the motronic, the maps are there, but it would indeed be a lot more difficult to tune them than with a stand alone - for a higher boost setup, to get the top end right, you have to move the data points around and retune everything - that's not terribly easy with the motronic with any software currently out there



are you still using the OEM MAF? that will be a limiting factor too - you won't get over about 330hp with the OEM unit



the intake manifold will also limit you up top



you've probably got as much power as you can get without major modification

Intercooling a Force Fed 968 - jfrahm - 04-18-2011

[quote name='flash' timestamp='1303066170' post='108582']

belt slip is not a reality or to be expected - it is unacceptable at any rpm the engine can generate - no belt should every slip - whether or not you choose to live with has nothing to do with the fact that it should not exist

[/quote]



Heh, well I won't argue with you. I live in a world of friction, entropy and decay and the fact is that belts slip. Tires slip also, just driving down the road.



-Joel.

Intercooling a Force Fed 968 - flash - 04-18-2011

well, i suppose you could say there is slip, in as much as there can be no perfect contact in a world of physical constants like we have, but that doesn't change that there should be no noticeable slip on this drive system - that belt should last as long as the others, and slip no more than the others

Intercooling a Force Fed 968 - rxter - 04-18-2011

"friction, entropy and decay"



Sounds like how I feel on Monday morning.

Intercooling a Force Fed 968 - DaveN - 04-18-2011

I'm sure they are words from Pink Floyds Division Bell album <img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" />

Intercooling a Force Fed 968 - tamathumper - 04-18-2011

Sounds like an ad for Viagra to me... [Image: blink.gif]

Intercooling a Force Fed 968 - craigawoodman - 04-18-2011

Flash,



The OEM MAF unit is gone, the new ECU does not need it. The boost levels are limited to the relief valve fitted on the output side of the compressor - want more boost, need to replace the relief valve, so the intercooler is not limiting boost (it could be providing "restriction" on the intake side of the engine).



What I have been told is to produce more power, I need to do two things;



1. Replace the blow-off/relief valve

2. Decompress the engine (larger head gasket)



This will allow more advance to be used with the engine and probably more boost prior to pre-ignition.



As the engine/set-up stands, adding more boost will be coutner productive as it will only cause more issues at high rpm.



Remember that this is a new engine with new knock sensors.

Intercooling a Force Fed 968 - flash - 04-18-2011

that relief valve should be able to handle 10psi easily - it is the same unit as used on the 951, which was 10psi - its only failing is heat and considerably higher boost - it should not pop at anything below 1 bar boost though, and as long as you keep it under about 200 degrees F, it should be fine



i don't know what heat that unit adds, but the one i am using doesn't add enough to need an intercooler - have you measured the pre and post charge temps without the intercooler?







Intercooling a Force Fed 968 - jfrahm - 04-18-2011

[quote name='flash' timestamp='1303160371' post='108664']

that relief valve should be able to handle 10psi easily - it is the same unit as used on the 951, which was 10psi - its only failing is heat and considerably higher boost - it should not pop at anything below 1 bar boost though, and as long as you keep it under about 200 degrees F, it should be fine



i don't know what heat that unit adds, but the one i am using doesn't add enough to need an intercooler - have you measured the pre and post charge temps without the intercooler?

[/quote]



He's talking about a boost limiter valve, which is like a wastegate for a supercharger system. Similar in function to a recirculation valve for operation under vacuum but set up with a spring to pop off under higher boost than you want to see at the manifold, allowing air to escape. Typically this is done with a MAP sensor or blow-through MAF based system so you are dumping unmeasured air. I suppose there might be one that recirculates also.



I'd be surprised if you have one and need a bigger one, I doubt there is a 4.5psi version that can adjust up to 6 or 10. I'd also be surprised if there was an issue with the recirculation valve (if that is what they were implying.) Those OEM valves work fine well over 1BAR and the same part is used on dozens of high and low boost cars.



Some people use an electronic valve that can be used to perform both functions, vacuum recirculation and boost limiting. I'm somewhat interested in this myself in case I want to limit boost under dangerous conditions or if the car is out of my hands for some reason.



-Joel.

Intercooling a Force Fed 968 - flash - 04-18-2011

hmmm - i thought he was talking about the valve the kit comes with, which is a bosch boost relief valve - i use the same one in my kit - it comes from the 951