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Originally Posted by 4x4le
Sorry. Im not trying to fill this thread with my results, I just want to clarify a few things. I didnt go back and optomise my low end, I actually didnt touch it much. Most of the pulls were started at a much higher rpm but this was the final one just to have a fuller graph. I know there is more work to be done and I will be back for more. I doubt I will do cams to be honest but I may some day. I think hitting numbers like that on a Dyno Dynamics with stock cams is just too impressive to add cams.
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It almost seems unreal on stock cams, considering everything I've ever seen with SR's (and that' nearly 8 years now myself, as I was KA before that). I can't think of a single other dyno near your 'power' (even with the big boost) on stock stuff hehe.
Quote:
Originally Posted by 4x4le
When I go back we will play with the load on the dyno to make the turbo spool more like how it does in real life and I will start the pulls at about 1800 rpm and go to about 5500 rpms and optomise all of that part of the maps.
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I do like the ability to load on the DD dyno...this is my single biggest complaint with the Dynojet we use.
Quote:
Originally Posted by 4x4le
After I go tune the lower rpms I will have a much more usable power band. Then If I were to add cams I would just be shifting that power band in favor or a higher hp number (which I have enough of right now).
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See, to ap oint...with the SR you can run a smaller duration cam and probably gain some 'airflow' in the midrange...not needing to boost as much would provide much less stress on the engine for sure...but then again at 9:1 with E85, 24 psi is nothing.
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Originally Posted by jspaeth
So, even if your torque drops off to say 250 ft-lbs in 2nd gear at high RPMS...you will be ACCELERATING equally as fast as when you are making 375 ft-lbs in 3rd gear.[
I myself, did not grasp this until I sat down and tried to understand it......unless your torque is dropping of REALLY fast, you ALWAYS (in our cars) want to rev all the way out to redline (due to the way our trannys are geared).
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While I can grasp your point, wouldn't we also need to figure in a 'time vs RPM' aspec to this? Having more power in a gear is nice, but lets just assume 3rd gear is a 2.5 ratio, and 4 is a 1.0. Even though you'd think the mechanic advantage in power production vs gear would be better in 3rd, could we also not argue that the time in gear in that 1.0 4th be better for total speed? (If this makes any sense)
Or is it just another factor in it all? Or am I just completly wrong hehe.
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Originally Posted by TurboB15sentra
It's tough to compare the transient response/spool up RPM, from dyno to dyno (even with the same car), as loading can vary wildly.
Travis
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Ah, another issue with 'dyno fights'...the time aspect. I love comparing some cars over 'time' in WinPep but even that is hard due to different start RPM and the sort between different dyno's. A lot of people don't understand that the 'big hp' number may be impressive, but once you change that lower variable to time (instead of speed) all sorts of new things can appear.
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Originally Posted by HemiCharger
Yeah but wasn't the GT28RS designed specifically for FWD sentra's? I have not seen any RWD SR guys running them. I like everyone else on here is running a GT2871R. I wish I would have gotten the GT3076 instead. You can always make more power with boost. I understand the desire for top end in our cars but why would you pick a .63 A/R over a .83 or whatever A/R? Is the peak really that BIG of a difference?
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The GT28RS was designed around the Miata, but adapted well to the Sentra. Remember that ugly brown 'disco brown' Sentra (hence disco potato) that was in every magazine ever 7ish years back?
Sure you can always make more power with boost...but you loose response. I'd take a faster spooling 400 hp anyday over a laggy 450. The numbrs may impress simple people, but it's all about performance in my spetrum.
A/R on the exhaust side is extremely important. If an engine doesn't breath alot, why run a big a/r and loose velocity? Run a smaller one, on a bigger compressor to make some good power. And is the peak difference that much? Not really...exhaust A/R in the 'generic sense' really doesn't in 'same family' turbos...not enough to make up for the lost spool up time. Now if you're throwing a turbo on a big cube car, then yes, you will then fight smaller A/R's choking motors.
Quote:
Originally Posted by jspaeth
From the results I've seen/heard, 0.63 vs 0.86 is maybe 500 RPM difference in spool up time, but I think the 0.86 will keep breathing for at least another 500 RPM higher than the other one.
Again, high RPMs is good, because you always want to be in the lowest gear possible at a given speed (given that the torque is not dropping off super fast).
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Yep. 500 to 800 rpm woth of spool up, with a 10-15 hp gain sometimes. To me, that extra hp isn't worth the loss of response, especially with a smaller frame turbo.