I think I want a blow job
08-27-2011, 01:43 AM
#22
Boost Pope
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That said, basing your turbo vs. SC decision on the fact that you already have a fancy exhaust manifold seems a bit short-sighted to me. I see no reason why you couldn't sell the manifold you have now to some kid over at CR.net, and that would eliminate your barrier to entry.
I'm trying to be objective here. You're starting with a worst-case-scenario engine (a high-compression 1.6 with unknown and presumably high-overlap cams) and saying you want to make more power on it with an M45 than a typical NB engine equipped with an MP62.
If I were you, I would seriously consider selling the entire engine and picking up a used stock 1.8 engine, preferably an NB. If you find the right buyer, you could probably break even on the deal.
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08-27-2011, 07:29 AM
#25
Uhm, ok. I was picturing something a bit more radical when you claimed 140HP.
Well, to be painfully honest, the motor you have now isn't exactly ideal for forced-induction of any kind. And a 10:1 engine is going to be even less tolerant of the scorching-hot output from an M45 than a stock engine.
That said, basing your turbo vs. SC decision on the fact that you already have a fancy exhaust manifold seems a bit short-sighted to me. I see no reason why you couldn't sell the manifold you have now to some kid over at CR.net, and that would eliminate your barrier to entry.
I'm trying to be objective here. You're starting with a worst-case-scenario engine (a high-compression 1.6 with unknown and presumably high-overlap cams) and saying you want to make more power on it with an M45 than a typical NB engine equipped with an MP62.
If I were you, I would seriously consider selling the entire engine and picking up a used stock 1.8 engine, preferably an NB. If you find the right buyer, you could probably break even on the deal.
Well, to be painfully honest, the motor you have now isn't exactly ideal for forced-induction of any kind. And a 10:1 engine is going to be even less tolerant of the scorching-hot output from an M45 than a stock engine.
That said, basing your turbo vs. SC decision on the fact that you already have a fancy exhaust manifold seems a bit short-sighted to me. I see no reason why you couldn't sell the manifold you have now to some kid over at CR.net, and that would eliminate your barrier to entry.
I'm trying to be objective here. You're starting with a worst-case-scenario engine (a high-compression 1.6 with unknown and presumably high-overlap cams) and saying you want to make more power on it with an M45 than a typical NB engine equipped with an MP62.
If I were you, I would seriously consider selling the entire engine and picking up a used stock 1.8 engine, preferably an NB. If you find the right buyer, you could probably break even on the deal.
The overlap isn't that radical. Besides the gears can dial some of that out. If not an M45. What turbo will start into positive pressure around 15-1800 and not run out of breath @7500
what do NB M62's make?
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08-27-2011, 01:06 PM
#29
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With a turbo. You will not make 200whp on an M45, it simply does not move enough air. I'd find a GT2554R, but even then you're not going to be making power at 7500rpm.
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08-27-2011, 01:23 PM
#31
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A little past 7k at best. It's a small compressor. It won't feel like a big turbo up top - my 2871R feels like a god damn freight train up top compared to this.
edit: This is my old setup, so
'99 longblock
BEGi mani/DP
stock IM w/ VICS switchover at ~5400
genuine GT2554R
eBay IC
MSPNP
Rx7 460s
~15psi
edit: This is my old setup, so
'99 longblock
BEGi mani/DP
stock IM w/ VICS switchover at ~5400
genuine GT2554R
eBay IC
MSPNP
Rx7 460s
~15psi
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08-27-2011, 01:49 PM
#33
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Don't know, never had the desire to spin my motor that hard. Could be doable, could fall off like a rock.
Be realistic with your expectations - you aren't going to find some random turbo that makes boost at 1500rpm but still pulls hard at 8k+. The 2554R will give you near-flawless response and still pull fairly well up top - everything bigger will give you a little more top end but impact the low-end and response in exchange.
Be realistic with your expectations - you aren't going to find some random turbo that makes boost at 1500rpm but still pulls hard at 8k+. The 2554R will give you near-flawless response and still pull fairly well up top - everything bigger will give you a little more top end but impact the low-end and response in exchange.
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08-27-2011, 01:53 PM
#34
Don't know, never had the desire to spin my motor that hard. Could be doable, could fall off like a rock.
Be realistic with your expectations - you aren't going to find some random turbo that makes boost at 1500rpm but still pulls hard at 8k+. The 2554R will give you near-flawless response and still pull fairly well up top - everything bigger will give you a little more top end but impact the low-end and response in exchange.
Be realistic with your expectations - you aren't going to find some random turbo that makes boost at 1500rpm but still pulls hard at 8k+. The 2554R will give you near-flawless response and still pull fairly well up top - everything bigger will give you a little more top end but impact the low-end and response in exchange.
The engine base should be able to fill in the bottom grunt some. So running a slightly larger turbo that didn't go positive until 2500ish would be alright. I just don't want to deal with an engine that all of a sudden "comes on" like Vtec.
I guess my main realistic power band is 4k-8k
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08-27-2011, 02:07 PM
#35
Boost Pope
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I'm not entirely certain that you understand the dynamics of how a supercharger works, so forgive me if I'm being obtuse, but I need to make sure we're all on the same page here.
Any given supercharger is capable of supporting a certain amount of HP. I think you may be under the impression that installing, say, an M45 on any engine will automatically raise that engine's output by 60HP or so, and that's completely inaccurate. A much less inaccurate (though still vastly oversimplified) explanation would that an engine with an M45 on it will make about 160 HP, regardless of what the engine started with. You take a 100 HP engine and put an M45 on it, you'll get 160 HP. You take a 250 HP engine and put an M45 on it, and power will actually drop to 160 HP.
Why is this?
Horsepower is made by burning fuel. And to burn a certain amount of fuel, you need a certain amount of air. If you move more air, you can burn more fuel and make more HP. Broadly speaking, it takes about 150 CFM of airflow (measured at atmospheric pressure) for every 100 HP you want to make.
Now, positive-displacement superchargers (and, to a slightly lesser extent, centrifugals and turbochargers) have a hard upper limit on how much air they can flow. For every rotation of the screw they move a certain volume of air, and just like piston engines, they have a redline. An M45 moves 0.75l (0.0265 CFM) of air per revolution, and it redlines at about 14,000 RPM. So that's a theoretical output of about 371 CFM. Unfortunately, Roots-style blowers in general are massively inefficient. You might get 70% efficiency out of the compressor itself at the flow levels you're talking about, plus another 30-35 HP in parasitic load just to turn the thing.
That's fine and well for relatively small, low-output engines turning at low RPM. But if (hypothetically) you were to put one of those on a 250HP V6, it would actually be a restriction.
The MP62 is better in all regards, but the combination of it and your engine still isn't going to make 200 HP. You are going to be detonation-limited by your high CR, and boost-limited by your cams. IOW, a lot of that air/fuel mixture that we worked so had to squeeze into the engine is going to blow right out your exhaust valves during the overlap period, and what's left is going to detonate.
what do NB M62's make?
No offense, but I don't believe that dyno chart for a moment.
so now the question at hand. What's the most cost effective way to force feed this thing with 6-10# of positive pressure
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08-27-2011, 02:20 PM
#36
Why is this?
Horsepower is made by burning fuel. And to burn a certain amount of fuel, you need a certain amount of air. If you move more air, you can burn more fuel and make more HP. Broadly speaking, it takes about 150 CFM of airflow (measured at atmospheric pressure) for every 100 HP you want to make.
Now, positive-displacement superchargers (and, to a slightly lesser extent, centrifugals and turbochargers) have a hard upper limit on how much air they can flow. For every rotation of the screw they move a certain volume of air, and just like piston engines, they have a redline. An M45 moves 0.75l (0.0265 CFM) of air per revolution, and it redlines at about 14,000 RPM. So that's a theoretical output of about 371 CFM. Unfortunately, Roots-style blowers in general are massively inefficient. You might get 70% efficiency out of the compressor itself at the flow levels you're talking about, plus another 30-35 HP in parasitic load just to turn the thing.
Horsepower is made by burning fuel. And to burn a certain amount of fuel, you need a certain amount of air. If you move more air, you can burn more fuel and make more HP. Broadly speaking, it takes about 150 CFM of airflow (measured at atmospheric pressure) for every 100 HP you want to make.
Now, positive-displacement superchargers (and, to a slightly lesser extent, centrifugals and turbochargers) have a hard upper limit on how much air they can flow. For every rotation of the screw they move a certain volume of air, and just like piston engines, they have a redline. An M45 moves 0.75l (0.0265 CFM) of air per revolution, and it redlines at about 14,000 RPM. So that's a theoretical output of about 371 CFM. Unfortunately, Roots-style blowers in general are massively inefficient. You might get 70% efficiency out of the compressor itself at the flow levels you're talking about, plus another 30-35 HP in parasitic load just to turn the thing.
100% VE = Ci x RPM/3456 (correct formula?)
so for me 1639cc = 100.01 Ci
rounding 100 x 7950 (potential RPM) / 3456 = 230.04
seems like it's on the edge of maxed out, but potentially viable
No offense, but I don't believe that dyno chart for a moment.
Cost effective meaning cheapest? That's easy. A Bell "Shangahi-S" turbo kit. $1,435 with the Chinese knockoff "T25/T28" turbo if you provide your own engine management (which you said you already had handled) plus whatever it costs you to hang an intercooler. And subtract whatever you sell your fancy header for.
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08-27-2011, 02:27 PM
#37
Boost Pope
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There is a sufficiently large body of empirical evidence to support the fact that an M45 is not capable of making 200 HP that you simply need to forget about it. You might be able to hit your power goals with an MP62 (emphasis on might) but it's very iffy, and would certainly not be cheap or simple.
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08-27-2011, 02:32 PM
#38
Don't interpret what I wrote literally. I was mostly just pulling round numbers out of the air from memory for the purposes of illustration.
There is a sufficiently large body of empirical evidence to support the fact that an M45 is not capable of making 200 HP that you simply need to forget about it. You might be able to hit your power goals with an MP62 (emphasis on might) but it's very iffy, and would certainly not be cheap or simple.
There is a sufficiently large body of empirical evidence to support the fact that an M45 is not capable of making 200 HP that you simply need to forget about it. You might be able to hit your power goals with an MP62 (emphasis on might) but it's very iffy, and would certainly not be cheap or simple.
I need to find the numbers. I do remember the 70% drop as a "standard"
using your numbers and this equation
REQUIRED AIRFLOW (scfm) = 2.723 x HP x BSFC
190hp with .5 BSFC would need 258.69 CFM. (still pondering)
these seem to agree with your memory (sort of)
http://www.rbracing-rsr.com/turbo/TurboMaps/M45flow.gif
http://www.rbracing-rsr.com/turbo/Tu...s/M45power.gif
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08-27-2011, 04:13 PM
#39
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benchtop racer... if you don't want to accept what people with experience and knowledge are trying to tell you... you'll just end up with a M45 and a detonating engine.
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