[craigawoodman]

With the debate and availability of kits to force induct a 968, what options have forum members pursued to intercool their modified beasts.



Intercooling reduces intake air temperatures, allowing more compression or fuel to be run - increasing power whilst at the same time (if the air and fuel mixture remains constant) reducing intake air temperatures to prevent pre-ignition (knocking) which will retard ignition and rob power and in the long term damage the engine and valves.



What have members done and why (i.e. intercooling simply as an insurance to reduce air temps, intercooling to increase boost pressures and chasing HP), what has worked and what has not - what mods have you had to do the car to make it fit, etc.



I am pondering this question myself as I have a SC kit installed. I am motivated to intercool the intake more from an insurance viewpoint given how hot the ambients are in Australia. Photo's would be good - part numbers and photo's would be even better.

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[craigawoodman]

In the interest of getting the topic kicked started, I have looked at a couple of options (none of which have been current thought through to actually working or being installed);



1. Lindsay Racing used to sell "Intercooler Tubes" - these are not on their website any more. THese were very small diameter water/air intercoolers with a separate water cooling radiatior, fan and water pump. This looked like a good packaging option - but as above - they are no longer available.

2. PWR Barrel Intercoolers - these have the benefit of being made (for me) in Australia. Not sure how to package or place these - but being water/air they do not have to be in the incoming air stream to the car. Thinking about running the compressed air down the RH side of the front of the car and then back up the LH side (will have to cut a hole somewhere) to the intake manifold. Possibl location would be behind the air intake duct at the front of the car. Web link http://www.pwr.com.au/?gclid=CJ7InZCcoaI...ucts/s=is/

3. Air to Air intercooler - limited front open air area, along with cooling air requirements currently required in N/A form - limit ability to remove heat at front of car. Not sure this can work.



We were told that a Mazda 3 Turbo Diesel intercooler would fit at the front of the car - this does not seem to be the case once the car was stripped.



I would like to keep the car standard (i.e. front bumper structure, etc) rather than cut up the front of the car. The car needs to remain road legal.

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[craigawoodman]

Found this website while searching for water to air intercoolers - this looks about the right size in terms of packaging apart from the cooling unit looks too big.



https://www.plazmaman.com/shop/?action=l...s&catId=23



Craig

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[Eric_Oz_S2]

Craig, I will be watching your install keenly as I have similar plans for the S2 - although the intercooler fitment is obviously easier on an S2.



Have you looked at using a Spearco intercooler? - these are used in the SFR kits. Obviously you will have differences because of the orientation of your supercharger (I presume) to keep the A/C. Perhaps you could try and find out which model SFR use, or perhaps even approach SFR themselves to supply an intercooler for you. Of course, your install will have its own problems that may not be solved by the SFR intercooler. I would be surprised if the Mazda 3 i/c would be of sufficient size, as they are only sized about 2 litre capacity. Has someone sized the i/c for your application?



If an intercooler is properly sized, located and matched to the system it will provide an improvement. If the kit is sized for no intercooler, then modifications will be needed to boost, fuel, etc as the intercooler will lean out the afr due to increased density. I presume you have this covered though by the new ECU.

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[flash]

there is a ton of information out there about intercoolers - oddly though there is no formula or data to tell you which one to run, or why



the first thing to realize is that every system operates differently - a roots blower does not work like a turbo and a centrifugal unit does not work like either - they all have their own idiosynchrocies



a centrifugal unit only generates about 12 degrees of intake heat per pound of boost (vs about 18 for roots and 25 for turbo), so its needs are a LOT less than the others



all intercoolers add intake restriction - this can cost you as much as 2lbs of boost - this is usually mitigated by adding more boost, and the fact that a cooler charge makes more power than a hotter one



a centrifugal unit determines its boost partly by the flow restrictions in both intake and exhaust - more restriction will mean higher boost levels, but generally less power at that boost level



most people who know centrifugal units will tell you NOT to intercool below about 7lbs



the first thing to do is measure your intake temps - then you get to decide if they are too high or not, and if adding an intercooler is warranted - then you get to determine how much heat you want to remove - this will vary depending on many factors - the net numbers may or may not justify an intercooler - as an example, on the kit i designed, at 5lbs there was no net gain to be had - at 7lbs it is questionable, but could probably result in as much as a 10-15hp net gain on a really hot day, but almost nothing on a cold one - at 10 lbs it is a no brainer



choosing an intercooler is complicated - the size and shape is critical to flow - you need to figure out how big it needs to be to remove the heat you want without adding too much restriction - this will take some trial and error



then you get to find a place for it - it needs to be in direct flow of cool air, and not where it would hinder the air to the cooling system - this is a common mistake people make - they stick it right up at the grill, but in front of the radiator - this causes 2 things to happen - the first is that they space the intercooler too far away from the radiator, which creates an airflow issue reducing the efficiency of the radiator - the second is that now they have pre-heated the air getting to the radiator, further reducing its abilities - this causes the engine to run hotter, which makes the intercooler have to work more, which makes the engine run hotter.............



the other item to consider is the plumbing of the intercooler and air filter - this must be as short as possible, and with as few bends as possible - it must also not have any sizing restrictions in it - you also must keep any hoses as short as possible, as they will expand and collapse, creating flow changes which result in restriction - aluminum tubing is far more effective than hose - this plumbing must also be kept away from any heat sources



the air filter is often overlooked - it must have adequate surface area to draw the air in - it must also be placed in a location where it gets the coolest air possible - it must also be located where it can be easily serviced - a forced induction system will draw a LOT more air than a normally aspirated system, and will require more maintenance on the filter - it is also much more important that the filter be clean

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[Dubai944]

I have the stock 951 intercooler which I have read from many sources is not the most efficient unit. Certainly it is thicker than ideal, but it is certainly convenient for fitment, at least in the 944 nose, not sure how it sits in the 968 nose. I have a cut out nose panel and the intercooler is ducted to make sure all the air going in the ducts go through, not around it.



Despite that I still see very high intake temperatures. My last weekend race the outside air temperature was about 35C (95F). Using the calculation suggested above my 10 lbs of boost adds approximately 120 degrees F of heat to the charge? I should put a temp sender before the intercooler to check this properly, but that would mean about 215 F or 101 degrees celcius going in to the intercooler. My intake temps after the intercooler on the weekend were up around 75 celcius or 167 farenheit, so thats a drop of 26 degrees celcius or 48 degrees farenheit. Did I do that calculation right? Darn I hate this celcius to farenheit conversion, why can't everyone just use metric! <img src="/forum/images/smilies/968/laugh.gif" class="smilie" alt="" />



Is that good?? What sort of temperature drop should we be aiming for with a really good air to air intercooler? Pete mentioned he had seen power loss and even temperature increase on a 968 using the stock 951 intercooler. Perhaps that was with lower boost and the stock intercooler is actually providing some worth on my setup..

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[flash]

i actually found the 951 intercooler to be very efficient compared to many others - on the roots car that i was working on, it did a much better job than the larger aftermarket cooler from SFR that it had in it when the car first came to me



the temp drop you saw is quite good - there are better units out there, and you might get as much as 60 degrees F out of it, if you get it in the right spot, but that's about it in real world



plumbing and placement is everything

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[craigawoodman]

Any comments on the benefit of water to air versus air to air intercooling (apart from packaging)?



Like Dubai944 - on a hot summer's day, the ambients can reach around 40C on the track. It is normal for forced induction cars (both turbo and SC) to lose power as the day heats up (sometimes dramatically).



I am leaning towards water to air because;



1. the actual intercooler is smaller and therefore easier to package in the nose - the radiator can be placed somewhere else

2. the pressure drop is much less than air to air

3. They work at all speeds

4. You don't need to route airflow to them (no need to cut holes in bonnets, remove bonnet latches, cut holes in the front structure, etc) - sorry for non-Colonial countries a bonnet is a hood - another English idiom.



Thanks,

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[flash]

water is a better conductor of heat than air - that being said, you have to have a source of cold water - that's a lot of plumbing back and forth to the separate radiator, pump, etc (unless you use ice)

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[RS Barn]

I will need to go over some notes from SFR kit with 951 intercooler. BTW we were testing in a very hot and humid period. Temps were in the mid 90's and humidity was 60% or so as I recall. It was hell at dyno. I think we were seeing 175F at charge side of intercooler and possibly 140F at intake with a 2.5psi boost drop. So 8.5psi off SC to 6 psi at manifold.

After removing intercooler and fabing an Aluminum charge pipe we had 8.5psi at SC and 7.5psi intake charge. Temps were 125F or so from SC and 105F at Throttle body. We also gained 25HP So intake charge was only 15 degrees higher than ambiant in extreme heat and humidity. We tuned a bit rich so car would be lean when weather was cooler.

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[flash]

yeah - intercoolers can result in odd things happening



i haven't figured out how to tap boost before and after the intercooler without welding on a bib for the lines to the gauges, and i haven't wanted to ruin some very expensive parts to do that - that would be cool though - i'd love to test some different types of intercoolers - it would be very helpful to see what was resulting in power increase, and what was just resulting in higher boost and/or higher intake temps, which with a centrifugal unit does not always equate to more power (but that's a whole different discussion)



lots of things affect temp - moving the air cleaner around can easily result in a 20 degree change in temp - one thing to remember is that any temp readings need to be done with the hood closed and the car on the road - when i was working on the development of the supercharger i found anywhere from 10 to 30 degree differences in intake temps from sitting on the dyno to running on the road, and some of those temps were varied dependent on the locations of the sensors - some sensors that seemed cool on the dyno were hotter on the road, and visa versa - it was really quite informative to see the airflow patterns in the engine bay, and what they do to some of the components in there - it was also fascinating to see how real sensors differed from the laser thermometer



fun stuff for sure

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[FraMac]

I've the intercooler mounted in front of the rad on my install - seems to work but could do with being bigger to deal with heatsoak, but that would be an awful lot of work for a relatively modest gain.

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[craigawoodman]

OK, some more interesting information on the 928 Motorsports supercharger.



The car is at the dyno being tuned.



1. We have had to order bigger injectors than the upgraded ones supplied with the kit. The engine is leaning out at high RPM.

2. We are running a double sided belt, so there is likely more air going to the engine at high rpm's than the stock kit - but the belt still slips (we will re-tension after the dyno runs).

3. The fuel pressure regulator has to be removed as it cannot keep up with the throttle when backing off and reduce fuel to the engine (over fuelling).

4. The ignition has to be retarded at high rpm as the engine is knocking.

5. Car is running around 4.5psi of boost (but has RSBarn high flow exhaust and Cat), so volume of air might be higher than this would suggest.

6. The supplied radiator fan is not worth s*** (mechanic's words) - the blade flatten out and it draw no air. Original fans are going to be re-installed.



So pretty much out of the kit purchased, we are using the head unit and the mounting hardware - almost everything else has had to be removed (including the air filter as we have used another one to allow the intercooler in the engine bay).



Remember that this is a brand new engine - so compression would be high, but we did not put in the thicker head gasket (which in hind sight would have been a good idea). Perhaps as the engine wears, the compression will drop slightly removing the issue with pre-ignition at higher rpm - we will have to wait and see.



It is borderline if the car will be ready for Bathurst, but regardless of whether it is finished or not, it needs to go on the trailer for the trip across the country.



This process will cost me an absolute bomb, but hopefully we might be able to get this to work.



THe intercooler is in, but the replacement boonet (hood) still needs to be cut, ductwork made and the whole lot painted (assumes they were able to get the system to work on the dyno on Friday).



Remember that this has been in process since January 10th this year and is still not finished.



Hopefully with the intercooler installed, and the tune set correctly, there will be a reasonable margin of safety.



Once I get to pick it up and drain my bank account to do so, I will post a full history of the saga.

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[Mark]

Over in the UK where A/C is not as big of a concern, and especially on a track car why not just got to neinmeister? He has done enough of these cars to know all the issues you would run into.

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[flash]

it sucks that you are having to deal with this - i'm really bummed that i couldn't put something together in time for you to have avoided all of this headache



1. yeah - i knew the fuel issues were going to be there at higher rpms - bigger injectors will bring their own problems into the equation, but a race car can generally ignore them, since you will be tearing that motor down every year - this is exactly why i did not get into this for a higher output kit - it's a whole lot of headache for very little gain



2. the pulley locations are going to be your enemy here - the double sided belt will help, but there is a limit to what it can do based on where things are - i assume you got rid of that stupid knurled pulley - that was a bad idea from the start (let's see, if i add what is basically a rat tail file to the back side of the belt, on a belt that slips, that should help, right?) - you may find that you need to add an intermediate pulley to add wrap and shorten the gap between pulleys



3. the OEM regulator should not have a problem keeping up - it sounds like the injectors are too big - or are you talking about that rising rate regulator? those do not generally work well - i would put in an AFPR in place of both of those



4. yes, you will find that the stock timing curve does not work well up top when you start making big boost - this is why i said that tuning was essential - there will be other challenges once you go stand alone, but basically you will have to figure out how to incorporate the condition sensors to accommodate changes - otherwise you will end up with a car that has very narrow operating conditions - you really don't need stand alone, if you can get somebody to tune the motronic - a piggyback might be the best ticket that would allow custom tuning, and retain the sensors



5. correct - an open exhaust will allow better flow, and therefore lower boost numbers, but give you higher volume - we found this when going from the stock exhaust to the rs barn cat-back - boost dropped a couple of tenths, but flow was noticeably improved



6. yeah - i saw that one coming - those things are fine for your 68 camaro that only spins at 5k and has an open underbody, but on a car designed to maintain negative pressure behind the radiator, they aren't going to work - it was bad enough that it was too small, left radiator surface uncovered, and even blocked some of it, and was single speed, but to have it flatten out and essentially become a block off, is a recipe for disaster



i would be a whole lot more worried about the supercharger heat than the intake heat itself - at 4.5psi, you shouldn't looking at that much intake heat, and an intercooler will add a lot of restriction and resultant pressure loss - there is really no reason to intercool a centrifugal unit below about 6psi, regardless of how hot it gets there, even on a track car - i would definitely measure the charge temps before mucking around with that - you could be right on the edge, but there are other things you can do that are a lot easier than an intercooler - unless that supercharger is adding more heat than normal, which is possible given that it is air cooled, i would look at other things - but again, definitely measure the pre and post charge temps to be sure

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[craigawoodman]

Flash,



Reply to some of your questions;



1. Aim is to have a very reliable engine and tune. By going to an aftermarket Engine Management Unit, we can control injector firing duration and therefore fuel delivery at all RPM and boost. By removing the rising rate fuel regulator and going back to a standard pressure, this will make it easier to tune.

2. Knurled pulley is gone, it was machined to accept a multi-vee belt. If anything, one of the next steps might be to have a larger crank pulley machined and a larger SC pulley machined to keep speeds the same but give more belt wrap to remove any slip.

3. As per 1 - the rising rate fuel regulator has to go.

4. The Engine Management Unit has more capability than the car has sensors, so this should not be a problem. It is an expensive option, but hopefully will provide reliability.

5. If the car has pre-ignition up top when running on a dyno, I would be worried about a hot day over here. Hopefully it is an insurance option for having the engine grenade under load on a hot day.



One of the issues here I think is the actual supercharger itself. When the belt was slipping, it was effectively stalling the air side of the unit. Not sure of the reason for this, but the unit is capable of running on a 5.0litre V8 engine, so it is possibly not able to run enough and the back pressure stalls the impeller. There has to be a reason for the much higher loads at higher rpm and I think it simply has to be lots more air volume (but an inability to make huge boost due to the units design). If you look at the 928 Motorsports dyno graph, power drops off after around 5,000rpm, when with a supercharger, it should continue to rise until nearly readline. I think this was two issues, lack of fuel and also lack of ability to flow the air through the engine and therefore the load on the supercharger lead to belt slip.



I don't have dyno numbers yet, but I am not chasing absolute power here, drivability (torque) and reliability will be key (you have to finish to win). Hopefully it will make reasonable power (above 350hp) and will be drivable at the upper limit of it's rev range (i.e. ok for the track).



But as per my last post, putting this kit onto your car and thinking it is going to work is a folly. If you get the supercharger to work and not slip the belt - you will lean out the engine in the higher rpm ranges and will eventually kill your engine.



Not sure what mess will be awaiting me on Monday, but hopefully it is back together, with most of the problems sorted out.



As for the Ninemeister option, it would be great, but where I am moving to (Perth in Western Australia), just had 60 days where the temperature was over 35 degrees celcius. Some of those days were over 40. So air conditioning is a must if you want to drive the car anywhere other than the track.

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[flash]

it gets over 40 here too, and i've tested mine on days like that, so i know it can be done - have hope - i haven't tested it on the track on days like that though



as long as the system you are going to use can recalculate for changing atmospheric conditions, then it will work fine - i still think it's overkill, but perhaps easier in the end than having to learn how to reprogram the motronic



if boost is falling off, and there is nothing in the design to limit boost at higher rpms (like mine does), then yes there is a problem with either flow or fuel, or belt slip



350 is going to be a real push - i think you will need about 8psi boost to get there at 7krpm

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[jfrahm]

Interesting. I can see it being possible to stall out the blower due to the large pile of air in front of it. Naturally the force required to turn it will go up in relation to the pressure ratio.



As delivered I had a little belt slip and I felt that the belt had to be run awfully tight to make proper boost, but I did see 6-7 psi when I put a boost gauge on. That was at 1650M / 5500' of altitude.



This was an otherwise totally dead stock car that actually did not shine on the dyno in the 'before' testing. To me, the belt slip was acceptable for a fun car that would not see track duty and I read that some belt slip was typical on other blown cars. In fact just like tires there is always going to be some slip and it is a question of how much is too much. I drove it several thousand miles with the blower on and always got where I was going. I did take the blower off once or twice and the car seemed to make good power stock. To my eye the head has not been off of this car and it has a little over 100K miles on it (some of which were spent crashing into things.)



As it is I have not worked on the project for a week or two, save making some drawings of what I want the next pulley profile to look like and the shape of the cutter I need to realize it. This next bit would probably be pretty easy for a machinist but I'm just a bloke with a secondhand lathe. The tricky bit is the tool room for cutting the precise grooves, and getting the angles set right on the tool post. I tried a test run on some PVC but it's too soft to get meaningful results.



I do not know what your pulley looks like but I tested a 52mm / 2.05" grooved alternator pulley I slotted and installed with a custom spacer bushing. The only other thing I did to that pulley was cook the anodizing off with oven cleaner (sodium hydroxide.) This pulley is not very suitable as the grooves are very deep and thus leave about 30% of the contact patch off the table. It slipped at 4.5psi or so, but it is also smaller in diameter by a fair bit than the stocker which also affects both contact patch and needed drive force. This pulley diameter is about the right size for maxing out the blower RPM and if I get good results with the custom profile I might try to make one this size as well with the matching profile to see if it'll hold boost a bit longer.



It'd actually be somewhat tempting to run this size pulley with another recirculation valve set for 4 or 5 psi as it makes so much boost down low the car is a blast to drive. I honestly had no idea I had belt slip until I could drive the car while watching the boost gauge. It flat out flew and the boost dropoff at over 4K was not noticeable on the street. In the stock config I saw 1 psi at 3000 rpm, with the 52mm pulley I got that at 2500 and 1.8 at 3000 rpms.



Performance was great stock so the best solution for me, I suspect, is to just improve traction on a stock sized pulley and go for a drive but it is my nature to see where the right edge of the graph is before backing off into the the butter zone.



Cheers,

-Joel.

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[flash]

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

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[FraMac]

I know that 9M had my car on an emulator for a whole day to get the optimum map for it (all part of the service). From recollection 68s run two different knock sensors - not a prob on my car (never been an issue) tho it needs to run on 98 octane (and I keep emergency octane booster in the dolly mixture box in the boot (trunk).

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