Ron Earp
05-12-2008, 08:47 AM
I thought some folks would be interested in my 260Z dyno plots so here they are. We’ve never pulled the 260Z before and figured before this weekend’s VIR race we’d get it and the TR8 on the rollers to see what they would do. The dyno runs were performed at a shop here in Durham NC that we use a lot and they run a Dynojet we’re familiar with.
The baseline pull for the 260Z was 152hp and 155tq, not very impressive. I proceeded to adjust the timing and make additional runs and also adjust the needle height on my carbs to balance EGT’s and A/F. We made about eight pulls and over time the motor became heat soaked with running temps around 200F. In comparison I run about 180-5F in races with a good radiator, oil cooler, and oil thermostat. We just couldn’t get the air flow to duplicate those temps.
After all the adjustments we came up with a best setup of 159hp and 162tq, but those gains were realized throughout the RPM range – not just at peak. I feel it was money well spent but I know that there is more power in this motor for sure. I think this motor would be a 80% IT type build (not meaning you are getting 20% more power from a 100% build!) – it was assembled well, with good components, new valves, springs, good balancing, etc. but certainly isn’t build to IT max specs. To give you an idea here are the areas that I think need improvement:
1)Rocker arm contact with valves needs to be optimized. Head prep/port/machining isn’t bad, but I’m sure it isn’t the equal of what the best Z builders have to offer.
2)Exhaust system needs to be reconstructed. I’m running through a muffler, about 92 dB sound, and the primary pipes on this header I feel are too large at 1 5/8”.
3)Carbs are still “off” – EGT’s can’t be balanced exactly and during my VIR race the car stumbled at a couple of places on track seriously costing me time/power. Didn’t do it on the dyno though, but the point is I’ve never experienced the 159hp/162tq on track I’m supposed to have.
4)Cam timing needs to be checked and made spot on. I’m using factory marks but have not verified this setup properly with a degree wheel. I did it once last year before my head gasket issue, but I think I didn’t do it correctly and it needs to be re-done.
5)And lots of other little things…..oils, spark plug indexing, air intake plumbing, and so on.
I understand that the higher hp Z builds (240s) will be around 175 hp and torque in that ballpark, so we’ve a ways to go. Still, I was happy with the dyno session and felt like I picked up some performance and a better understanding of the motor.
R
The baseline pull for the 260Z was 152hp and 155tq, not very impressive. I proceeded to adjust the timing and make additional runs and also adjust the needle height on my carbs to balance EGT’s and A/F. We made about eight pulls and over time the motor became heat soaked with running temps around 200F. In comparison I run about 180-5F in races with a good radiator, oil cooler, and oil thermostat. We just couldn’t get the air flow to duplicate those temps.
After all the adjustments we came up with a best setup of 159hp and 162tq, but those gains were realized throughout the RPM range – not just at peak. I feel it was money well spent but I know that there is more power in this motor for sure. I think this motor would be a 80% IT type build (not meaning you are getting 20% more power from a 100% build!) – it was assembled well, with good components, new valves, springs, good balancing, etc. but certainly isn’t build to IT max specs. To give you an idea here are the areas that I think need improvement:
1)Rocker arm contact with valves needs to be optimized. Head prep/port/machining isn’t bad, but I’m sure it isn’t the equal of what the best Z builders have to offer.
2)Exhaust system needs to be reconstructed. I’m running through a muffler, about 92 dB sound, and the primary pipes on this header I feel are too large at 1 5/8”.
3)Carbs are still “off” – EGT’s can’t be balanced exactly and during my VIR race the car stumbled at a couple of places on track seriously costing me time/power. Didn’t do it on the dyno though, but the point is I’ve never experienced the 159hp/162tq on track I’m supposed to have.
4)Cam timing needs to be checked and made spot on. I’m using factory marks but have not verified this setup properly with a degree wheel. I did it once last year before my head gasket issue, but I think I didn’t do it correctly and it needs to be re-done.
5)And lots of other little things…..oils, spark plug indexing, air intake plumbing, and so on.
I understand that the higher hp Z builds (240s) will be around 175 hp and torque in that ballpark, so we’ve a ways to go. Still, I was happy with the dyno session and felt like I picked up some performance and a better understanding of the motor.
R