What boost do you run?
- Thread starter barks944
- Start date
So most people use 15% as a thumbnail guide. Although our Porsche Club use 32% and I have a sneaking suspicion that this would be as per the factory. However the club uses this for all versions of Porsche to calculate wheel and crank power figures to put us in the appropriate class.
George Elliott
New member
Thanks Nick. I will have to intercept one of the S2's with rotten sills en-route to the crusher and put the block on the shelf....[
]Just on the power calculation comments, has anyone used a dynolicious app on their phone, [
] honestly - for a tenner its amazing, and I think quite accurate. Put it like this, the ultimate practical measurement is to weigh the car and measure the time it takes to accelerate.One other question which I'd value you gents comments on ref a 951 mod engine. You may be aware when Honda made the Accord diesel engine, they moved the crank c/l so that the con-rod vertical was 6 degrees past 12 0'clock. (so "TDC" was +6deg to true TDC). This was to assist the smoothness of a very high compression. I really like the idea, and reckon if the guys at serdi were asked to move the liners to create this they could, but am not sure if the cylinder head would cope with the out of position which ensued...??
regards
George
PSH
PCGB Member
Hi George
I have the Pocket Dyno+ app on my phone which I've found very accurate although I haven't weighed the car to work out the BHP. It can give a very accurate 1/4 mile using it's GPS, I was just looking at the result page but seems I must have lost them during an update, there's no cars listed in the garage either ...lol IIRC I had 0-60 times of low 4 secs, 0-100 around 10 and 1/4 mile low 12's. all this on roads so should be better on a track. These times are what I'd expect from the car with it's mods, would be nice to test again when the new mods are measured, We'll see...
Regarding the Honda engine situation I'd bet that if it can be done Serdi are the people to do it, amongst other things mostly F1 tech they have a lot of experience in liner mods. I remember John showing me a couple of Diablo engines that were having liners fitted, evidently the engines as they come out of the factory are crap, there's a design flaw that means a rebuild will be needed at very low mileage, Serdi's mod solves that problem. Since they did a lovely job on my block I'm happy to recommend them, btw Serdi were the engineers that did the work on Andrew S's 422bhp car many years ago.
regards
Pete
I have the Pocket Dyno+ app on my phone which I've found very accurate although I haven't weighed the car to work out the BHP. It can give a very accurate 1/4 mile using it's GPS, I was just looking at the result page but seems I must have lost them during an update, there's no cars listed in the garage either ...lol IIRC I had 0-60 times of low 4 secs, 0-100 around 10 and 1/4 mile low 12's. all this on roads so should be better on a track. These times are what I'd expect from the car with it's mods, would be nice to test again when the new mods are measured, We'll see...
Regarding the Honda engine situation I'd bet that if it can be done Serdi are the people to do it, amongst other things mostly F1 tech they have a lot of experience in liner mods. I remember John showing me a couple of Diablo engines that were having liners fitted, evidently the engines as they come out of the factory are crap, there's a design flaw that means a rebuild will be needed at very low mileage, Serdi's mod solves that problem. Since they did a lovely job on my block I'm happy to recommend them, btw Serdi were the engineers that did the work on Andrew S's 422bhp car many years ago.
regards
Pete
PSH
PCGB Member
ORIGINAL: 333pg333
If I pulled off the Pools/Lotto I'd get a billet block/head/crank made then boost to 35-40psi like all the competitive Japanese crowd do.
That's a big little word though...'IF'....[
It's not only the Japanese cars that are boosted higher Patrick, my son's Cossie is at 36 psi. Does make me wonder how they can hold that amount of boost without blowing up as he's not had any major problems with the engine, the gearbox however is another matter...
I would expect my block with it's full Raceware bolts/studs and other mods should be able to take more boost but the question is, 'how much?', perhaps I'll find out one day...
Pete
George Elliott
New member
my turbos engine has spat a piece out of its camshaft housing gasket!
[/quote]
Tom, sorry to hear that - how is the crankcase vented, you sure there is no excessive pressure?
George
944t
[/quote]
Tom, sorry to hear that - how is the crankcase vented, you sure there is no excessive pressure?
George
944t
ORIGINAL: PSH
ORIGINAL: 333pg333
If I pulled off the Pools/Lotto I'd get a billet block/head/crank made then boost to 35-40psi like all the competitive Japanese crowd do.
That's a big little word though...'IF'....[
It's not only the Japanese cars that are boosted higher Patrick, my son's Cossie is at 36 psi. Does make me wonder how they can hold that amount of boost without blowing up as he's not had any major problems with the engine, the gearbox however is another matter...
I would expect my block with it's full Raceware bolts/studs and other mods should be able to take more boost but the question is, 'how much?', perhaps I'll find out one day...
Pete
It's harder to run higher boost the bigger your cylinder capacity gets, but the usual tricks apply. On the modified Cosworth blocks they run longer studs deeper into the block to keep the head on. They also modify the sumps, not sure if this is for baffling or just to run more oil.
Hilux
New member
ORIGINAL: TTM
I'm sure you will get nothing but positive results. When will that be ready?
You may have seen it already, here is the dyno sheet from a friend's 3.0 engine with the Lindsey intake.
When a standard 968 turbo S makes a remarkable 368 lbs.ft (500 N.m) at 3000 rpm with the 951 intake, he sees that even earlier at 2700 rpm and it spreads up until 6100 rpm. Apart from another friend's 1200 bhp muscle car, this is the fastest car I have ever been in. Mine is no slouch but his is borderline insane.
May I assume the graph is not fully calibrated as it has the torque/power crossover at about 4750rpm which is wrong.
TTM
Well-known member
To run a lot more boost than the popular 1.2 bar limit often heard about, we would certainly need to modify the quench area to improve flame front propagation thus avoid preigntion and/or detonation. The design of the std 944 2V head is not too far from that of a manhole cover... [&:]
George Elliott
New member
[]
any thoughts on Crankcase venting TTM? to atmosphere via a Catch can or to Intake system?
I personally dont like the vent to atmosphere as it seemed to cause gaskets to weep but I tried it as the Sci Vision did not like oil contamination.......
George
944t
]any thoughts on Crankcase venting TTM? to atmosphere via a Catch can or to Intake system?
I personally dont like the vent to atmosphere as it seemed to cause gaskets to weep but I tried it as the Sci Vision did not like oil contamination.......
George
944t
TTM
Well-known member
Definitely back into intake sytem pre compressor inlet, in my opinion.
Vacuum in the crankcase will always help against bottom end seals sweating oil, and will also assist oil in getting properly through the turbo's center housing back into the sump (which is why I think Porsche draw a vacuum line between the engine mount and the AOS), otherwise oil may leak out though turbine seals - this is more likely to happen when running a cone filter instead of the AFM, as the AFM, when closed, pretty much prevents any air from being sucked into the turbo apart the air coming out of the crankcase. When running a cone filter, the turbo will naturally suck the air from the filter more easily than that coming from the crankcase, particularly at tick over (when the AFM is about fully closed on a std engine).
I use a recirculated catch can in between, which shouldn't really be needed when pistons rings are near new and properly sealing, but it should further avoid oil vapour making its way back into the turbo inlet. I emptied it today and though there was not much in it, there was still a little bit of the typical mixture of oil/fuel coming out.
If you use a good recirculated catch can then the MAF sensor should not be affected at all. I use a Saikou Michi unit and it works pretty well. I would always widen the hole coming out of the top of the AOS, as it's actually a fait bit smaller than the size of the hose suggests, when you look carefully into the hole.
Vacuum in the crankcase will always help against bottom end seals sweating oil, and will also assist oil in getting properly through the turbo's center housing back into the sump (which is why I think Porsche draw a vacuum line between the engine mount and the AOS), otherwise oil may leak out though turbine seals - this is more likely to happen when running a cone filter instead of the AFM, as the AFM, when closed, pretty much prevents any air from being sucked into the turbo apart the air coming out of the crankcase. When running a cone filter, the turbo will naturally suck the air from the filter more easily than that coming from the crankcase, particularly at tick over (when the AFM is about fully closed on a std engine).
I use a recirculated catch can in between, which shouldn't really be needed when pistons rings are near new and properly sealing, but it should further avoid oil vapour making its way back into the turbo inlet. I emptied it today and though there was not much in it, there was still a little bit of the typical mixture of oil/fuel coming out.
If you use a good recirculated catch can then the MAF sensor should not be affected at all. I use a Saikou Michi unit and it works pretty well. I would always widen the hole coming out of the top of the AOS, as it's actually a fait bit smaller than the size of the hose suggests, when you look carefully into the hole.
Well hopefully the new motor to go into my car will have reduced some of the symptoms we're discussing here guys. Large headstuds, deckplated, linebored and dry sumped. Interestingly with the dry sump you don't vent to atmosphere. In fact if you do need to ventilate the block it's to draw in air, not vent. The Oil tank is used as the catch can if you can call it that. You can vent the oil tank if needed. I believe this depends on the type of oil pump and how much vacuum it's creating. From what I'm told (from the US builder) my motor was producing about 10-15" Mercury and thus didn't need an air inlet. We will have to monitor this again when the motor is back in the car and on the dyno. I know there is a little bit of questioning of U.S. power figures. I think Sid was working on a similar theory as someone in this thread previously. Based on mph, weight and possibly elevation (?) he came up with over 500whp with his stroker build. It is generally accepted that this mode of establishing power is pretty close. While he uses his car primarily as a test mule and for drag racing I imagine that my motor will have some superior components and therefore should expect somewhere in the vicinity of where he's at. I would think we could run 1.6 bar pretty easily with the hardware on this motor. Of course that all counts for very little should the tuning be off. Glad the people we are dealing with here are experienced with all sorts of high hp race / drag cars. The funny thing was when they were tuning the 2.5L motor they asked what c/r the motor had. "10:5...11:1 ?" You could have knocked them over with a feather when I told them 8:1 haha. The new motor is similar and will be running on race quality E85. I actually believe we could run 2 bar pretty comfortably...But I have no need to do this. When we were running 1.4bar in the 2.5L the car felt pretty damn quick (on the day of the crash). I remember thinking that I didn't need too much more power than this basically stock motor was producing. I am hoping that the 3L will allow us to run around on a low 1.2 bar +/- and rely on the torque that all the extra cc will produce plus the vastly improved V.E. that will come from the much better head, cam, extractors and we will go with a slightly reduced exhaust size also. Plus the car will be lighter again without the rear glass and metal fenders on all corners being replaced by lighter alternatives. Add to this some significant aero improvements. Car promises to be very fast. Just need to rid the driver of the ring rust that has probably crept into his repertoire! [&:]
Posts made and opinions expressed are those of the individual forum members
Use of the Forum is subject to the Terms and Conditions
