jagman Posted October 15, 2010 Share Posted October 15, 2010 How do you know what the vvti is doing , is the solenoid controlling oil pressure correctly . maybe not an mechanical issue but a control issue , perhaps a boost guage in the exhaust manifold and compare intake pressures with exhaust pressures would give a clearer picture of whats happening and explain the spool being slow Im Not really au fait with the vvti system to be of much help ,,, Quote Link to comment Share on other sites More sharing options...
Miguel Posted October 15, 2010 Share Posted October 15, 2010 I have now been told it has a 1.2mm head gasket, so the already low standard 8.5 to 1 compression is even lower, which won't help his soggy response. A HKS 1.2 mm HG keeps the CR at 8.5:1:) Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 15, 2010 Share Posted October 15, 2010 Stock factory gasket is 1 mm, and about .9 mm compressed. Quote Link to comment Share on other sites More sharing options...
Miguel Posted October 15, 2010 Share Posted October 15, 2010 Top of the page> http://www.hkseurope.com/engine/apps/headgasket.htm Quote Link to comment Share on other sites More sharing options...
dandan Posted October 15, 2010 Share Posted October 15, 2010 Probably drops to about 8.48:1 Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 15, 2010 Share Posted October 15, 2010 I have seen my micrometer, which I trust more than an HKS advert I also cite: http://www.titanmotorsports.com/grmehega.html if we are looking at ads What's the stock combustion chamber volume, I can't find my notebook just now. Quote Link to comment Share on other sites More sharing options...
Miguel Posted October 15, 2010 Share Posted October 15, 2010 That's something you would need to take up with HKS Europe. Last time I spoke to them they quoted that their head gasket thicknesses are stated in a compressed state. If it's worth anything, I vaguely remember my micrometer spitting out similar measurement to yours for an N/A head gasket with the TT being around 1.4mm in uncompressed form. I'm more than willing to be proved wrong as that was some time ago and my memory is not what it was. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 15, 2010 Share Posted October 15, 2010 I am 90% sure I am right as I do a lot of Skyline engines and I recall that both they and the 2JZ-GTE have 1.00 mm head gaskets as stock. I could go and see if I have an old one, but I am too idle Quote Link to comment Share on other sites More sharing options...
Digsy Posted October 15, 2010 Share Posted October 15, 2010 Assuming the stock head gasket is 1mm thick compressed, with an 86 bore and stroke and a prefect 8.5:1 CR the compressed volume required would be 60.663cc. Keeping the compressed volume the same and increasing the head gasket thickness to 1.2mm would drop the CR to 8.37:1 This also assumes that the hole in the head gasket is 1mm bigger than the bore to allow for alignment tolerances. Quote Link to comment Share on other sites More sharing options...
Lee P Posted October 15, 2010 Share Posted October 15, 2010 I measured a stock TT head gasket and it was around 1.4mm uncompressed. I did all this when I built my engine and I was working out the CR. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 15, 2010 Share Posted October 15, 2010 From memory a stock TT head combustion chamber volume is around 58 cc? So with a 1.2 mm gasket the CR comes out pretty low. I did a quick calculation using piston volume negative figures as cited by CP and by JE. JE list 2JZ-GTE pistons as having a bigger bowl volume than CP. I have no idea what pistons are in this though. Personally, from looking at Julian's torque graphs it looks similar to other set ups with this turbo and I guess his and my idea of too much lag aren't the same as others perhaps? Did you have a drive in the thing Lee? What did you think of it? Quote Link to comment Share on other sites More sharing options...
Lee P Posted October 15, 2010 Share Posted October 15, 2010 I didnt drive it, but went in it. There does seem to be very little power low down (off boost) but when it comes in its fine. The TDI graph looks quite close to others with the same turbo although again it does seem to be lacking power very low down. Changing the exhaust cam had little effect on the spool, it just seems to be a sluggish engine. If you dont rev it high enough when you change gear it falls off the power band, which is strange for this size turbo. I will have a measure of a stock head gasket Chris as I have one here, just to make sure. From memory a stock TT head combustion chamber volume is around 58 cc? So with a 1.2 mm gasket the CR comes out pretty low. I did a quick calculation using piston volume negative figures as cited by CP and by JE. JE list 2JZ-GTE pistons as having a bigger bowl volume than CP. I have no idea what pistons are in this though. Personally, from looking at Julian's torque graphs it looks similar to other set ups with this turbo and I guess his and my idea of too much lag aren't the same as others perhaps? Did you have a drive in the thing Lee? What did you think of it? Quote Link to comment Share on other sites More sharing options...
J_Boulton Posted October 15, 2010 Author Share Posted October 15, 2010 I thought you said it was laggy before? Unless that was someone else. We only changed the springs didn't we? If so then no. No, it was springs and valves, plus any other necessary bits. It was basically all the Supertech stuff that was due to go onto your head but ended up going on mine. The GT4088R setup I had previously had good low down power. Michel, Ryan and others could all vouch for that. Quote Link to comment Share on other sites More sharing options...
Miguel Posted October 15, 2010 Share Posted October 15, 2010 I will have a measure of a stock head gasket Chris as I have one here, just to make sure. Can you have a measure the gasket bore too please bud? IIRC the stock is 87 and the HKS is 88. Quote Link to comment Share on other sites More sharing options...
Lee P Posted October 15, 2010 Share Posted October 15, 2010 Can you have a measure the gasket bore too please bud? IIRC the stock is 87 and the HKS is 88. The stock is more than 87mm, I will have a measure up tomorrow some time. Quote Link to comment Share on other sites More sharing options...
Miguel Posted October 15, 2010 Share Posted October 15, 2010 Thank you. Quote Link to comment Share on other sites More sharing options...
Miguel Posted October 15, 2010 Share Posted October 15, 2010 From memory a stock TT head combustion chamber volume is around 58 cc? I think Tony Licence measured his around 44cc with aftermarket valves. Quote Link to comment Share on other sites More sharing options...
Wez Posted October 15, 2010 Share Posted October 15, 2010 Interesting stuff Quote Link to comment Share on other sites More sharing options...
Lee P Posted October 16, 2010 Share Posted October 16, 2010 Ok, I measured the stock tt head gasket and it's 1.4mm thick uncompressed. The bore size is 87.5mm That would probably make it around 1.35mm compressed. This means fitting a 1.2mm gasket would very slightly raise the cr. Quote Link to comment Share on other sites More sharing options...
J_Boulton Posted October 17, 2010 Author Share Posted October 17, 2010 Right, so if cr is possibly not an issue does it now seem logical to do a test of swapping the turbo for a similar one, like Ian suggested? If so, which one? I still have my GT4088R but the blades are frayed and I know it's down on power because of that, but would it at least give me a comparison on the spool and lag? Or is there another one to test which would give a better comparison and go on easier, with maybe less hassle? My money is still on a turbo problem, must be driving you insane trying to get to the bottom of this. Yeah, you're right Jamie, it'll be a room with padded walls for me soon if I don't get it sorted. Quote Link to comment Share on other sites More sharing options...
JamieP Posted October 17, 2010 Share Posted October 17, 2010 Might be worth sending the GT4088 to AET to get repaired, once you have tested it out you can always sell it on afterwards then. Quote Link to comment Share on other sites More sharing options...
Lee P Posted October 17, 2010 Share Posted October 17, 2010 Im not saying the CR is not a problem in your case, just that a 1.2mm HG is smaller than stock. Other things can affect CR, like head work. Swapping the turbo is a good idea as this will eliminate another possabilty but you do need to fix the blow on the t4 flange as this will effect spool. Right, so if cr is possibly not an issue does it now seem logical to do a test of swapping the turbo for a similar one, like Ian suggested? If so, which one? I still have my GT4088R but the blades are frayed and I know it's down on power because of that, but would it at least give me a comparison on the spool and lag? Or is there another one to test which would give a better comparison and go on easier, with maybe less hassle? Yeah, you're right Jamie, it'll be a room with padded walls for me soon if I don't get it sorted. Quote Link to comment Share on other sites More sharing options...
J_Boulton Posted October 17, 2010 Author Share Posted October 17, 2010 I'm pretty certain it's not a genuine Garrett exhaust housing as it hasn't got a little plate on giving part/serial numbers, etc. Do you think they would still be able to repair it economically if that's the case? Or are they just going to say to me it's not genuine, they can't do anything with it and I'd need to buy a new one. Quote Link to comment Share on other sites More sharing options...
J_Boulton Posted October 17, 2010 Author Share Posted October 17, 2010 Im not saying the CR is not a problem in your case, just that a 1.2mm HG is smaller than stock. Other things can affect CR, like head work. Swapping the turbo is a good idea as this will eliminate another possabilty but you do need to fix the blow on the t4 flange as this will effect spool. Yeah, sorry Lee, I knew you weren't actually saying it's been ruled out as a problem, I'm just trying to think of the next best thing to do. I'll get that new gasket fitted today. Quote Link to comment Share on other sites More sharing options...
JamieP Posted October 17, 2010 Share Posted October 17, 2010 I'm pretty certain it's not a genuine Garrett exhaust housing as it hasn't got a little plate on giving part/serial numbers, etc. Do you think they would still be able to repair it economically if that's the case? Or are they just going to say to me it's not genuine, they can't do anything with it and I'd need to buy a new one. It will only cost you the price to post it to them to ask there opinion on it. Quote Link to comment Share on other sites More sharing options...
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