Dummy Run: 3.0T vs 2.5T
04-19-2004 | 07:37 AM
#17
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Originally posted by Songzzz
fast951> Do you think I should start with 2 degrees retard?
fast951> Do you think I should start with 2 degrees retard?
If your chips are not custom tuned for a 3.0L, be careful with boost!!!!!
04-19-2004 | 01:04 PM
#19
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Hey Fast-
What about a 3.0L makes it more sensitive to timing? Is it the fact that there is less dwell time at TDC due to the larger stroke and shorter rod/stroke ratio? I would think that with less dwell at TDC you would have a smaller range of rotation to choose from on timing, and thats why a 3.0L would be more sensitive. But this is speculation.
I have read that a long stroke short rod engine like the 3.0 will be less prone to detonation in that it passes TDC faster. Although possibly the larger flexibility in timing of the 2.5 would allow you to run more retard and effectively have the same or better threshold of detonation. Again, Speculation.
What about a 3.0L makes it more sensitive to timing? Is it the fact that there is less dwell time at TDC due to the larger stroke and shorter rod/stroke ratio? I would think that with less dwell at TDC you would have a smaller range of rotation to choose from on timing, and thats why a 3.0L would be more sensitive. But this is speculation.
I have read that a long stroke short rod engine like the 3.0 will be less prone to detonation in that it passes TDC faster. Although possibly the larger flexibility in timing of the 2.5 would allow you to run more retard and effectively have the same or better threshold of detonation. Again, Speculation.
04-19-2004 | 04:20 PM
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Back to the injector spray pattern issue – think about how the fuel is sprayed into the intake runner / head port – why would you want 90 degrees? That will just wet the walls on the intake ports. If you look at the pattern of the Siemens injectors and figure the distance from the injector to the valves you will see why a tight pattern makes sense.
Chris White
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04-19-2004 | 05:59 PM
#22
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Surely its hard to combust a jet opposed to a mist. More atomisation. 90 degrees was perhaps a little high, however, why would companies like Delphi and Bosch make their injectors to spray in a mist? For fun?
04-19-2004 | 11:30 PM
#25
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Originally posted by fast951
Before you turn up the boost on the 3.0L make sure the chips you have timing that is 3.0l friendly. Turbocharging a 3.0l requires special attention to timing!! If you are using a 2.5l chips better run high octane (race gas) in it before turning up the boost at the dyno.
Before you turn up the boost on the 3.0L make sure the chips you have timing that is 3.0l friendly. Turbocharging a 3.0l requires special attention to timing!! If you are using a 2.5l chips better run high octane (race gas) in it before turning up the boost at the dyno.
04-19-2004 | 11:39 PM
#28
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Re: Dummy Run: 3.0T vs 2.5T
Songzzz,
I'm sure you will out-run 2.5s once you are all dialed in. To your point, however, my 2.5 is running so good right now that I was wondering over the weekend if I was crazy to be building a 3 liter. I am running race gas and 23 psi these days, and the car is unreal. I was making 305 or so at 18psi on street gas, which felt strong, but at 24psi with race gas, the car just explodes with acceleration. I just keep telling myself that I can add 20% across the board with a 3 liter. Let us know once you are broken in and dialed in. I don't think you can get a real feel for the car at .8 bar and/or while keeping it under 5k rpms.
I'm sure you will out-run 2.5s once you are all dialed in. To your point, however, my 2.5 is running so good right now that I was wondering over the weekend if I was crazy to be building a 3 liter. I am running race gas and 23 psi these days, and the car is unreal. I was making 305 or so at 18psi on street gas, which felt strong, but at 24psi with race gas, the car just explodes with acceleration. I just keep telling myself that I can add 20% across the board with a 3 liter. Let us know once you are broken in and dialed in. I don't think you can get a real feel for the car at .8 bar and/or while keeping it under 5k rpms.
Originally posted by Songzzz
Break-in almost done by now so I up the boost to 0.8 Bar, street-tune using the LR Mafterburner and arrive at 13:1 (0-5psi), 12:1 (5-10psi) and 11:1 at 12psi, which I am happy for the meantime. Car runs great so I ask a friend out for a spin, just to compare the difference. It's a modified 88' 951 running on K27/6, MAP, 1.4Bar, guesstimate to be around 290 at the wheels.
Side by side, we floored it from rolling start, the 3.0 is very much quicker in the lower rpm and gears, particularly below 4K. By the end of 3rd gear, the 3.0 leads by 5-6 car length. 4th gear onwards, from 3K to 6K rpm, the 2.5 closes in rapidly and eventually overtook the 3.0 in a flash. Point to Note: the 3.0 revs to only 5000 as a run-in precaution
It seems the 2.5's max power is around 5500 rpm, while the 3.0 peak HP sooner.. maybe around 4500rpm but HP seems to take a dive thereafter.
Well, we are only guessing right now. Both cars will be dynoed next week.
Conclusion: $$ is better spent properly building a 2.5L so as to rev and boost higher. However, the 3L is the better car to drive in town.
Break-in almost done by now so I up the boost to 0.8 Bar, street-tune using the LR Mafterburner and arrive at 13:1 (0-5psi), 12:1 (5-10psi) and 11:1 at 12psi, which I am happy for the meantime. Car runs great so I ask a friend out for a spin, just to compare the difference. It's a modified 88' 951 running on K27/6, MAP, 1.4Bar, guesstimate to be around 290 at the wheels.
Side by side, we floored it from rolling start, the 3.0 is very much quicker in the lower rpm and gears, particularly below 4K. By the end of 3rd gear, the 3.0 leads by 5-6 car length. 4th gear onwards, from 3K to 6K rpm, the 2.5 closes in rapidly and eventually overtook the 3.0 in a flash. Point to Note: the 3.0 revs to only 5000 as a run-in precaution
It seems the 2.5's max power is around 5500 rpm, while the 3.0 peak HP sooner.. maybe around 4500rpm but HP seems to take a dive thereafter.
Well, we are only guessing right now. Both cars will be dynoed next week.
Conclusion: $$ is better spent properly building a 2.5L so as to rev and boost higher. However, the 3L is the better car to drive in town.
04-19-2004 | 11:59 PM
#29
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From: Taiwan/Singapore
NZ> international trade, I sell DSP chips and ProAudio devices.
Tom> How's your project coming along? After 800 miles and 2 oil change, I up the boost to 1 Bar last night. Full boost ~3500rpm @ 3rd Gear, lost traction a bit. Still trying to dial AF in, way too rich now.. 10.5:1 in the 4.1 to 4.3v range.. 9:1 from 4.4v onwards. All I can say is that I really enjoy driving the car now, its a street-daily driver where low-end responsiveness is an asset.
Tom> How's your project coming along? After 800 miles and 2 oil change, I up the boost to 1 Bar last night. Full boost ~3500rpm @ 3rd Gear, lost traction a bit. Still trying to dial AF in, way too rich now.. 10.5:1 in the 4.1 to 4.3v range.. 9:1 from 4.4v onwards. All I can say is that I really enjoy driving the car now, its a street-daily driver where low-end responsiveness is an asset.