Well I can notice the extra little bit of power, but I can also tell the idle isnt as smooth as it used to be. I hope this isnt going to be too hard on the engine :wacko:
what did you end up doing bout the timing mark? did you compare the underdrive pulley to the stock unit? much difference?
Yes I did check it John It was out by 5 degrees. I put the old one back on and rotated it till the timing mark was at zero. Then slipped it off and put the OD pulley on and the mark was exactly 5 degrees out. I remarked it and bolted it up. I had one issue John, One of the belts wasnt the right one, there is meant to be a 970 to 1000mm one in the kit (the one that goes over the waterpump, alternator and crank. The only one left that wouldnt fit was 785mm long. I had to buy another one to replace it! $20 :wacko: bugger
Is the rough idle a constant thing? Mine seems to fluctuate a bit when the AC is off, but from memory I don't think the installation of the underdrive caused this. One of my belts was wrong too, that was a bit off a bugger at the time, late on a Sat. arvo! It might take a day or two to notice the difference as the computer learns its there! Mine coupled with POD made 11.7KW difference. Added headers & total difference was 31.9KW Once again it took awhile for the computer to adjust to it.
I just sold my headers cause I bought a turbo engine to cannabalize for parts, so i can do a low boost turbo setup. The pod filter was a great upgrade, instantly better. I intend to run the underdrive for a few days and see where it gets to. I agree about your comments. Sometimes it seems ok but others rough. I put some Nulon octane booster in the optimax last night. That seemed to make more difference !! :thumbsup:
shit sorry. my mate who's a mechanic got them for me, i just assumed they'd be good. i'll hook up with you and reimburse.
Low boost IU am still piecing together info for this but it occurs to me that with the standard NA engine running 10.4:1 conmpression it will be able to stand a small amount of boost. If the internal pressure under boost during compression isnt ridiculously highg, The NA engine should be OK I would think. There are heaps of other cars with standard engines that run 5 to 7 PSI of boost and survive just fine. So the idea here is to low boost the NA engine to say 7 psi and enjoy. Most of the TT's are running over 12psi. The last question I have is regards intercoolers. aparently at low boost intercoolers dont have that much efect. I may just run straight from the turbo's to the Throttle bodies. See how that goes before changing front bars and piping etc.
don't think its a great idea to skimp on the intercooler, especially as you are running higher comp ratio. all possible steps to reduce/prevent detonation should be taken. 7 psi will give a pressure ratio of about 1.5. assuming a 75% turbo efficiency (anyone got a compressor map for the stock turbos?), this will give a temperature rise of around 50 deg C on a 25 degree day. higher at max loads. hence compressor output will be at 75 deg. an 85% efficient intercooler will bring this down to 33 deg, which equates to an increase in charge density of around 15%. i haven't considered the pressure loss across the ICs however. given the increase in charge density, the benefits in suppressing detonation, and the fact that there is an IC system ready to go, i think it'd be well worth going to the extra effort.
I think that you hit the nail on the head about the losses through the IC, If the insertion loss is 3psi, then if I run 7psi boost, I have lost about 40% of the boost pressure. Now if I am running 12psi of course I have lost 25%of the boost pressure. The VL turbo commodore had a high compression ratio and no intercooler, so I spose there is a precident there. I really have to get a look at the engine before I formulate a plan. Any help sorting the logical parts of this is really appreciated guys.
yeah but i think in the case of the vl it was more a matter of cost cutting. new ford falcon xr6t has an intercooler, and thats only running 5psi boost (8.7:1 comp ratio). what is the logical part you talk of. probably missing something, but would think it'd be pretty straightforward to wack on the IC and piping, especially for a man of your crafty nature! just get a tt front bar, or even better update (2000 spec or stillen gtz-r are my choices). will try and put some more numbers together with pressure losses.
i suppose if we were to include pressure loss across the IC, we'd run a pressure ratio of 1.6 (to see 1.5 in the plenum, assuming a 2psi drop across the IC). this will give a temperature increase of about 56 degrees C. a 85% efficient IC will bring this down to a 9 degree increase. this will yield an increase in charge density of 15%. then factoring in the pressure drop this will be about 12%. still well worthwhile me thinks. anyone have any actual figures on stock intercooler efficiencies and pressure drops?
