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Old 01-27-2012, 05:10 PM   #21 (permalink)
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Swapping the whole trans would be easier. You have to pull the trans out and open it up to swap gears, and you only have to remove the trans from the car if you're swapping.

The HF has a taller top gear, and it also has a different ring and pinion ratio ("final drive") so that every gear is even taller than it would be in a DX or an Si transmission.

The DX (standard) and Si actually have the same gear ratios, but the final drive ratios are different which effectively gives the Si shorter gears all around. The individual gears for the HF are all taller (except possibly for reverse?) and the final drive is taller as well.

-soD

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Old 01-30-2012, 05:58 PM   #22 (permalink)
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Quote:
Originally Posted by some_other_dave View Post
Swapping the whole trans would be easier. You have to pull the trans out and open it up to swap gears, and you only have to remove the trans from the car if you're swapping.

The HF has a taller top gear, and it also has a different ring and pinion ratio ("final drive") so that every gear is even taller than it would be in a DX or an Si transmission.

The DX (standard) and Si actually have the same gear ratios, but the final drive ratios are different which effectively gives the Si shorter gears all around. The individual gears for the HF are all taller (except possibly for reverse?) and the final drive is taller as well.

-soD
yeah the gear swapping is a ninja task lol. I may consider it myself to keep power and still have good cruising MPG. But my feeling is that this is not your concern? then why hook up vtec? it will only hurt your MPG. Vtecs only purpose is power. Bigger cam lobes and more fuel and timing = less MPG. honestley your better off without it
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Old 01-30-2012, 08:11 PM   #23 (permalink)
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My interest is the vtecE which does help fuel economy
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Old 01-30-2012, 08:12 PM   #24 (permalink)
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...supposedly
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Old 01-30-2012, 08:22 PM   #25 (permalink)
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My interest is the vtecE which does help fuel economy
yeah I dunno. to my knowledge vtec has always been about power. efficient power by allowing 2 camshaft profiles, one for mid range normal driving and the other for power. combined they make the most power and fuel efficiency you can get out of these small motors. but take the vtec out and I believe you will get better mileage. just make sure you have a way of tricking the ECU so your not running the check engine (closed loop) program, or you will have terrible mileage.

I suppose you can make or brake the theory by testing it yourself.
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Old 01-30-2012, 09:12 PM   #26 (permalink)
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As I understand it, the vtecE is a little different. Instead of using more gas to get more power it drops to 12 valves instead of 16 and goes into lean burn to use less gas when cruising under 2500 rpm. That is the first stage of the engine. The second is the normal 16 valves and is really no different from any other D15 engine, but the third stage is standard vtec and is exactly what you are saying. More power from a smaller engine by switching the cam shaft profile. At the moment I have hooked up the different profiles to switches I can control manually, but really the lean burn is the part I'm most interested, but I need to have the actual ecu for that. I have noticed a small boost I in fuel economy when I keep the car set to stage 1 without too much loss of power though, so that's cool. As for the third stage, you're right, I'm not terribly interested in it, and I never get the rpms high enough to acutely use it, so I may just opt against it.
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Old 10-31-2013, 03:50 AM   #27 (permalink)
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any update?

how did this turn out? has anyone successfully mated a d15b with vx intake and exhaust incl 5 wire sensor and vx cat, coupled to tall hf tranny? i found the thread informative but vtec-e/ecu issues seemed unresolved. thanks for any update

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crx hf, crx si, d15b, d15z1, engine swap

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