Supercharged QV (take 3)-or is it a turbo?

I know what your saying here, but I think you need to consider some other factors. And take note that I am no means any real expert, just observant.

First of all, as I have bumped along, I have been more and more coming to the conclusion that 4 valves dont necessarily make more power. But they do seem to have better low end power and hold it over a wider range, and they are good for emissions. Also, I think what we get with a Ferrari is the name, but not necessarily thier top engineering. In going over my own 308, and in talking to people at Wiseco, Norwood, and others, as well as many people here and elsewhere, Ferrari seemed to have built these engines in a way to drastically detune them.

On my particular motor, the pistons come up to TDC and stop .055" below the top of the liner. Wiseco confirmed that on all the 308 motors they have made pistons for, they were all in that same range, QV's included. While my engine had 9.7:1 Borgo pistons, it actually only made a calculated CR of only 7.9:1, Stock pistons would never net anything close to the 8.8:1 Ferrari claimed, more like 7.4:1 or less. Perhaps this is why they work so well turboed???

The cylinder heads have the exhaust ports offset from the header ports by 4mm, and are drastically large in comparison to the intake, and quite a bit larger than the header port. Some have said this was done for emissions reasons, to create turbulence for the air injection. For a factory hell bent on racing, and attempting to sell an image of thier accomplishments, it had to be hard to be forced to detune thier engines further and further to comply with world wide regulations.

I honestly believe that if owners had raced 308's on the track, and developed aftermarket components to improve the cars braking, handling, and power, it should be highly capable of whipping any 911. Its liquid cooled, and the architecture is there to make a lot of power. But Ferrari were also trying to package the motor back there under that deck lid, so maybe thats why it has such screwed up heads. I don't know. Your 800HP Chevies have some pretty radical heads over stock so I dont know if thats a fair comparison, and all of the jap cars, while capable of making huge amounts of power, are not able to stay together at those amounts for any period of time.

So where is the power? Again, not a big expert here, but just looking at this motor in comparison to others, it "looks" like it should be able to make quite a bit. I personally worked on a Renault 813 engine, that was highly modified for ice racing. This would be the hot Renault engine for a Europa, and thats actually what this engine ended up in. The heads were ported, high CR pistons, pair of 45 DCOE's, header, and a very very hot cam. The motor idled at about 1500 and was very loud and rough. Gassing it would immediately send the tach past 5000. While it was never dynoed, the general feeling of those involved felt it was making over 200 HP. That motor was 1565 cc, so roughly half a 308. But it had pushrod valve train, and I doubt the head could ever be worked to flow like a 308 could, it just was a tiny and short head.

So, I think if you took a good streetable figure of 120HP per liter, NA, our 308's should be "able" to produce in the neighborhood of around 360, but most probably wouldnt like it as it would be far to peaky. So backing off to 100 HP per liter, makes a good streetable figure. As you are wanting to supercharge yours, it will be interesting to follow your discoveries of the cylinder head. I really think this is where the engine will make its power.

 

I have used special porting epoxy to correct inlet ports near the valve seat area, and the epoxy lasted well. I seem to remember that thy also made an epoxy for exhaust ports.
(I think it was a Moroso or a Manley product.)
I am sure that it would work for a naturally aspirated engine, but I am not so sure on the exhaust temps when a supercharger is put into the mix.

 

Mark, any thoughts on stock compression? Are you still running stock pistons? I thought you changed when you did the 2nd blower.

I never calculated my old one, Krowbar's number of .055" below the deck is correct though (I think I got .056, regardless). I don't remember the head cc off hand (around 30 maybe). To get to 11:1 we had to run a touch above the deck to make up for the valve pockets.

 

I measured 40.5 cc chamber volume on my 2 valve heads which was a number Wiseco also had. So along with that and a good head height I have heads that were never milled. I have no knowledge of the QV head volume.

Brett, I am curious how high above the deck you went? I should be about .010" above if I recall, with 10.4:1 CR. But these new pistons have some pretty radical pockets and I think I may carefully mill off the sharpness of the pocket edges, so as not to have any hot spots.

I would also be interested in hearing opinions on coatings, like on piston crowns. I know they work short term, but what about long term durability, flaking, etc. I am also somewhat concerned with the idea of a straight stainless steel exhaust valve, vs sodium filled. Would new sodium valves offer any real benefit and or, is straight stainless durable enough in our applications?

 

We had a set of 12 pistons coated a while ago for a Diablo engine we were hopping up a little. We had anti-friction coating applied to the skirts and a high temp coating applied to the piston tops. We were experimenting with some special rings that turned out not to want to seat and wound up taking the pistons out after only a short time. We were amazed at how quickly the coating was disappearing after such a short time. With all the oil that was being pumped through the combustion chambers you would think, air/fuel ratio being the same, the pistons would not be running that hot.

One thing I've considered doing to my(supercharged) 308 engine next time I take it appart is to install spray jets to cool the pistons from below with motor oil. It's not a new concept but it shouldn't be too hard to rig something like that up to keep the pistons alive under boost.

One problem with putting large non-aluminum (epoxy,etc) lumps in the exhaust ports might be that it acts as an insulator, possibly making problems with uneven expansion in the head. 308 heads are already prone to cracking.

I've supercharged two engines before this one with great results but still consider myself a novice at that end of it. I've only had a few chances to check in on this thread but I'm really impressed with the mental processes going on here. It's been great reading. Inspiring reading.

 

I was reading that idea, and while I wasnt thinking insulation, it didnt seem like something that would stay there very long. I thought of an aluminum tube type insert, like Mk e suggested. But again I wasnt considering it being an insulator, more I thought it would be a really good place for corrosion to start. So is the best way to solve the problem really only to weld the port up? I have never liked welded up heads, but if there was a good enough performance gain I might consider it. Then I could re-center the port so it flows directly into the header. Does anyone have a ball park idea what this would gain for power?

 

krowbar, I have wisecos for my 4v, definitely grind down the pocket edges. They provide the pistons somewhat unfinished (like most other one offs I suppose). I used a dremel to smooth/round the edges of the pockets and then just polished polished polished on a wheel until they're mirror-like.

.010-.015 above the deck is about where I'm at, compressed head gasket was .050 or .055 IIRC. I have all the exact numbers at home, it's been awhile though.

 

Being a government employee and all, I've been wondering about most bang for the buck. It's been mentioned before that perhaps just opening up the intake side might be the best way to go, especially with a view toward reliability (Very big with me) based on the recent exhaust concerns.
If the head could be done with just the intakes done to an open 348 oval spec and simply better match the exhaust header to the port and clean up the injector, that seems like the best overall fit. If I could target a reliable 265 - 270 rwhp / 215 - 230 rwft-lbs from a na 3.2 4 valve, that would be the ultimate street engine for me.
Looking forward with great anticipation to the flow numbers.
best
rt

 

Interesting project Mark.

I have one going on myself. I bought a complete spare engine and trans on Ebay and have decided to make the next one twin turbo with a 50 shot of NOS to reduce lag. The ball bearing turbos should help as well and bring on hp sooner. I am wondering if working the heads is worth it? for 40-70hp it is not worth it to me. It seems the gains should be more?

cheers

paul

 

Out of curiosity, what if you could use an a/c evaporator as part of an intercooler? Or why couldn't you?

 

I thought it might be the case. When we charge an a/c system we usually get the air temp down to about 40 degrees or so. I wasn't sure if by using two seperate evaporators on the a/c system and switching off the cab a/c and turning on the evaporator in the intake would be of benefit or not. This is a very interesting thread.

 

Garret turbo on the car now. I do not know the trim sizes. I will have to look at the original invoices.

This turbo is going to be swapped for a hybrid ball-bearing T3/T4 60-1 Hi-Fi w/ P trim .81 dry/standard cart. This will increase the air flow considerably and bring on the boost 300rpm or so sooner. At 18 psi I am anticipating another 80rwhp. James at Norwood says this is the right turbo for the car. I have been told it will pull strongly to 8000 rpm without giving intense "shock load" to the transaxle. I can give up a little boost response in an effort to save the transaxle.

The TT turbo project will involve hotter cams, lighter cam followers, stronger valve springs, billet rods, twin ball-bearing turbos, Motec, and a 50 shot of NOS to get things rolling. I bought a set of headers on Ebay that look horrible from the factory. I was hoping to use these with the new engine. The were obviusly made before a mandrel bender. I do not know of anyone that makes headers for a turbo 308 application? I am thinking that you and I could benefit from some headers that flow much more effeciently than the euro headers. Look at the ripple in the pipe in the link below. Not good for flow!

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1,1&item=4600064092&sspagename=STRK%3AMEWN%3AIT#ebayphotohosting

 

I would have replaced the turbo at Norwood had I known it was not the ideal setup. James told me this after I outgrew 14 psi. I would ship it in a heartbeat but the last time i did that it came back with a ding in the front fender. 42lb. injectors on the car with two fuel pumps, secondary comes on at 10psi. I have way too much fuel right now which is ok since I am going to up the boost to 18 with the new turbo.

fuel pressure and duty cycle i do not recall? I can get that off the Haltech? 60 psi sounds right but not absolutely positive.

Bigger headers would be a great benefit that is for sure.

 

Garret T04 is all it says on my invoices from Norwood.

 

I think you want a little valve over-lap to help cool the exhaust valves. Besides, how else are you going to make those big flames out the back?

I have a couple of junk 2 valve heads if you ever need one.

Good luck on your mission. It'll be interesting to learn what you discover chopping up that 4 valve head.

Wil