Si weight loss thread

grantsjc

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OK so some of advantage that Si has over CTR is lower weight. And I'm of belief that the SI has a lot of weight loss potential. Lower weight means free horsepower per lb and better handling . So in initial assessment I see following areas of opportunity

Body: Steel hood and trunk replaced by dry carbon pieces
Drivetrain: lightweight flywheel
Brakes: aluminum hat two piece rotors
Suspension: aluminum body coilovers, hollow swaybars, aluminum suspension arms
Wheels: lightweight 17x8 wheels with light summer tires
Exhaust: titanium or lightweight steel cat back system.
Electronics: 9 lb Lithium battery

I'd bet that's close to 200 lbs of weight loss potential

More radical steps

Sport steering wheel no airbag
Carbon fiber race seats

Has anyone weighed Si wheels and stock cat back exhaust? Just curious how much they weigh.
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5inn

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jpuhl777

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I appreciate weight loss and I certainly put ultra light weight wheels on my car, not opposed to carbon fiber panels and that stuff. Titanium exhaust, all for that! But I wouldn't start removing interior pieces like seats. It doesn't really improve things enough to be without those items.

Unless you're going full on race car that is....
 

bahndrvr

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IN all honesty - The rims AND tires, and the Cat/Downpipe would probably be your biggest weight loss items and the lightweight flywheel as we have Dual mass and I would venture it's over 20bs and has natural rev hang due to this. But catless downpipe, flywheel, and lighter rims and tires would make a pretty damn big difference! The hood and trunk as well, beyond that it probably wouldn't amount to much. When you remove your cat assembly throw it on the scale, you will be suprized how much it weight!!!
 

5inn

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IN all honesty - The rims AND tires, and the Cat/Downpipe would probably be your biggest weight loss items and the lightweight flywheel as we have Dual mass and I would venture it's over 20bs and has natural rev hang due to this. But catless downpipe, flywheel, and lighter rims and tires would make a pretty damn big difference! The hood and trunk as well, beyond that it probably wouldn't amount to much. When you remove your cat assembly throw it on the scale, you will be suprized how much it weight!!!
If you downsize to 17x8s, you can save ~60lbs in just wheel weight alone.
 


integra15

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The hood weighs a ton. I am surprised there is not a CF one available already.
 

bahndrvr

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As of now - had similar issues in the past with other manufacturers and cars - I'm not going to increase the power for a while so won't need a clutch or flywheel, by the time I get to the flywheel issue it will be long since worked out. My E46 BMW was the one that had the issue before and within the first 18 months they had if fixed and they are much harder to tune than Honda, alot more locked down etc.
 
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grantsjc

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Have you looked at mufflers and all steel pipes on OEM muffler? Id say there is at least 25-30 lbs of weight savings in deleting resonator and twin mufflers and going to straight back design with small muffler without making a ton of noise given these cars are turbo. Front hood is really heavy too, at least 10 lbs of savings there. Battery probably 10 to 15 lbs of savings depending on how radical you go with lithium cell. Again I see Si as being better handling car than stock CTR potentially if roughly 200 lbs of weight can come off. Id not want to touch interior but lots of stuff that can reduce weight without impacting cars day to day usefulness. Im pretty good at eliminating weight on cars. Took my 3000 lb Porsche Cayman S to 2150 lbs and my 2900 lb Porsche Boxster to 1900 lbs. So seems like taking a 2900 lb Honda Si to 2700 lbs should be pretty easy. Especially given weight savings in wheels available if using 17x8 easily 50-60 lbs there. First 200 lb should be very easy. Then it gets tougher and you need to make sacrifices with its street worthiness. I like doing stuff you cant see easily .

Si at 2700 lbs with a +6 psi tune and sticky ax tires, bigger rear bar would be pretty impressive handling car and would be pretty quick in straight line too without risking too much of that Honda reliability.

I bet someone figures out how to overcome flywheel issues .
 
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bahndrvr

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wesgoood

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If you downsize to 17x8s, you can save ~60lbs in just wheel weight alone.
I've really been tempted by this in all honesty. Just because 17" is also such a good sweet spot financially. I'm curious if anyone in this thread has pics of their Si's on some nice 17"s and 235/45/17 tires? I've only really seen them on the hatchbacks.
 

anzoategui@2218

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Im pretty good at eliminating weight on cars. Took my 3000 lb Porsche Cayman S to 2150 lbs and my 2900 lb Porsche Boxster to 1900 lbs. So seems like taking a 2900 lb Honda Si to 2700 lbs should be pretty easy.
I agree that dropping 200# should be relatively straightforward. Given your Porsche experience, how specifically would you go about taking the Si down to, say, 2250#?
 
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grantsjc

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I agree that dropping 200# should be relatively straightforward. Given your Porsche experience, how specifically would you go about taking the Si down to, say, 2250#?
That would require gutting interior, removing AC system, replacing body panels with dry carbon fiber panels, replacing windows with thin plexiglass, lightweight carbon race seats, lightweight steering wheel. If dedicated track car then lots of engine accessories could come off, titanium studs and lug nuts, remove e brake, pin hoods and get rid of all locks and hinges, Get rid of headlights if no night driving, get rid of heater core and ventilation system . Id bet I could get this car under 2000 lbs as a time attack car. Wouldn't be much good for anything else though!
 

anzoategui@2218

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That would require gutting interior, removing AC system, replacing body panels with dry carbon fiber panels, replacing windows with thin plexiglass, lightweight carbon race seats, lightweight steering wheel. If dedicated track car then lots of engine accessories could come off, titanium studs and lug nuts, remove e brake, pin hoods and get rid of all locks and hinges, Get rid of headlights if no night driving, get rid of heater core and ventilation system . Id bet I could get this car under 2000 lbs as a time attack car. Wouldn't be much good for anything else though!
Something to give to Compass Racing or the equivalent for the conversion then. I'm guessing that would likely run a minimum of $50K, with the one-off cf panels costing a decent chunk of that. Cost aside, the lighter the better when it comes to putting anything on the track.
 

jpuhl777

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Lighter is "good" but "balance" is best, don't forget about that part. removing a lot of weight in the rear on an already nose heavy car will for sure impact the handling.
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