RobPhoboS Posted August 20, 2019 Share Posted August 20, 2019 This is going to be a bit of a long post, apologies ! 2004 350z - DE - 135k (burning a bit of oil but no streams of smoke! - full bottom end rebuild this coming winter - funds pending) Dyno session 1 Over Christmas I did my timing chain (no issues before, just age/mileage) and I decided to do cams (JWT C8), springs, revup oil pump, water pump etc. On the first dyno session, aside from these things done the car had stock headers, stock intake, straight pipes, cobra sports y-pipe back (2x 2.5" to 3", then 3" back). Intake temp:10 deg (Feb) 310bhp (@fly)(it's a comparison to my first dyno there back in Nov 2012) WHP/AFR Dyno session 2 The next dyno session I had added the following by this point: Kaaz 1.5 diff Z1 'Race' intake with the large 6" velocity stack and filter Kinetix Velocity 75mm TB Note - the very first runs we did had the stock intake connected, we noticed it was down and thought it was odd. So I then installed the Z1 intake but the dyno was the same. So my initial conclusion was that the Kinetix was causing the loss but clearly started to extend the power curve further to the right. hmmm I had assumed (with a couple of other folks) that my car could breath in properly but not out, however it doesn't seem that was really the full issue. Intake temp: 24 deg (May) 292bhp (@ fly) WHP/AFR Dyno session 3 PPE long tube headers (JWT advised spec on these). HP Ignition coilpacks (decided to refresh them as I had original ones on the car). Fresh plugs. Motordyne XYZ-pipe with resonator. Intake temp: 25-27 deg (Aug) 300bhp (@fly) Pink line is from May, so you can see the PPE's have gained at the lower end at least. Knock detection disabled (was troubleshooting idea) Once again comparison to Feb (WHP) Ok, so we made the low end come up nicer now, and the curve itself looks quite nice - however, the numbers aren't, in comparison to my initial run of the year. Jez also disabled the knock sensor for a couple of runs too, just in case that was causing a problem, it made a few more hp but nothing obviously wrong there. This seems like either the Kinetix is struggling for some reason (but hasn't on other cammed NA cars - it stretches the power curve to the right), or something else has gone wrong (timing?). Engine parts as of August 2019: Uprev tune Kinetix Velocity plenum JWT C8 Cams & springs Z1 3" Race intake with 6" velocity stack/large filter Ferra stem seals PPE Longtube headers (spec advised by JWT) RevUp oil pump Motordyne resonated Y-pipe 3" back Cobra Sports resonated exhaust New waterpump/timing chain/gallery gaskets/o-rings etc Stock heads/bottom end (rebuilding in winter) Stock injectors HP Ignition coils I did a dry comp test back in Nov, the results were around 185-195psi. After doing the cams this year my compression was down to around 155psi. JWT said that the pressure would be down perhaps by 15psi but not to this extent. So maybe I didn't do the November testing correctly (I'm sure I did) but with this current one I know I did it properly for sure. I decided to do a wet compression test, followed a day later by a leak down test, here are my results: Wet Comp was about 7% more than dry (around 165psI). Leak Down (I'd imagine anything over 8% isn't ideal but I knew the rings are worn): So that confirms what I knew anyway, the rings are worn (no problem as bottom end stuff is waiting to go in). I couldn't hear any obvious air leaking or bubbles in the coolant overflow. Could that result just be a mix of the C8's/rings and the relatively low HP readings due to rings ? I've messaged back and forth with a few of you on here (plus JWT and the US forum), and your input has been hugely appreciated ! 1 Quote Link to comment Share on other sites More sharing options...
davey_83 Posted August 20, 2019 Share Posted August 20, 2019 (edited) Are you still using the stock fuel pump? If so fueling at top end may be at its limit. Edited August 20, 2019 by davey_83 Quote Link to comment Share on other sites More sharing options...
RobPhoboS Posted August 20, 2019 Author Share Posted August 20, 2019 1 hour ago, davey_83 said: Are you still using the stock fuel pump? If so fueling at top end may be at its limit. Yep still stock fuel pump and injectors (I do plan on changing injectors but wasn't sure about pump). I was initially thinking that the timing could have been out by 1 tooth as someone on the US forum had the same problem, and almost same parts. They had it on the ex cam chains (no sensor for exhaust unfortunately on DE). Quote Link to comment Share on other sites More sharing options...
G1en Posted August 20, 2019 Share Posted August 20, 2019 Did Jez say how much the intake temp effects power? worth asking as 10deg to 25deg could be significant. Quote Link to comment Share on other sites More sharing options...
davey_83 Posted August 20, 2019 Share Posted August 20, 2019 I'd say the cams are bleeding off the compression, so I'm surprised to see the C8's noted as suitable for stock bottom end. Seems higher comp pistons are need to pull back what's been lost. Quote Link to comment Share on other sites More sharing options...
RobPhoboS Posted August 21, 2019 Author Share Posted August 21, 2019 11 hours ago, G1en@waxandshine said: Did Jez say how much the intake temp effects power? worth asking as 10deg to 25deg could be significant. Yep, he did say that the dyno figures that out, and you can go see the difference it calculates. As to how accurate it is, we're not totally sure. However, yes it's quite a difference in conditions! (more so for humidity iirc) 10 hours ago, davey_83 said: I'd say the cams are bleeding off the compression, so I'm surprised to see the C8's noted as suitable for stock bottom end. Seems higher comp pistons are need to pull back what's been lost. I guess technically the C8's fit and work but like all aftermarket cams, not optimally out of the box. I didn't expect the difference to be quite like this, granted the rings clearly aren't helping eh. Thank you for taking a look Quote Link to comment Share on other sites More sharing options...
davey_83 Posted August 21, 2019 Share Posted August 21, 2019 I had Tomei Poncams fitted to my Almera GTi SR20DE and these were a plug and play application, with gains throughout the rev range so it is possible to do. For a more track focused application, sacrificing low end for middle and top seems a given. Re the timing, I don't think you'd be making the power you are being a tooth out. However if you've read similar issue over the pond, it might be work a check. I doubt you'd gain any more knowledge from here than what Jez would have told you at the time sadly. However I'd personally look towards fueling as no doubt the fuel pump and injectors will be working very hard to keep up. 1 Quote Link to comment Share on other sites More sharing options...
evilscorp Posted August 21, 2019 Share Posted August 21, 2019 your reduced compression is definitely going to loose you quite a bit of power. If the injectors or pump were an issue I would expect the graph to fall off a cliff when maxed out or show a different Air fuel ratio but all looks normal. add some 11:1 comp pistons and it should pick up well at the top end. Very good thread though, nice to see the different effects that each engine change brings. 2 Quote Link to comment Share on other sites More sharing options...
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