[flash]

our cars start out with 236 hp (SAE like the dynos here measure)

factor in compression loss from age (185lbs at the cylinder is about 10% loss) = 212.4 hp (or a whopping 23.6 hp loss)

factor in effective change due to the junk we drag around (say 50lbs - you'd be surprised how easy that is) = 209 hp

factor in octane drop running 91 instead of 93 (like here in california) = 205 hp

don't get me started on the effect of heavy wheels, tires, and big brakes

it's no wonder we have hyundais passing us

you can see that, while weight and fuel play a part, the largest loss is in condition of the engine - keep the compression up and keep your power - relative to things you would do to your car for power, obviously this is one of the most expensive propositions, but all the bolt on tweaks in the world (chips and such) won't make as big of a difference as a valve job

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[Jamie '92 968]

<!--quoteo(post=81671:date=Oct 12 2009, 11:56 AM:name=flash)-->QUOTE (flash @ Oct 12 2009, 11:56 AM) <{POST_SNAPBACK}><!--quotec-->our cars start out with 236 hp (SAE like the dynos here measure)

factor in compression loss from age (185lbs at the cylinder is about 10% loss) = 212.4 hp (or a whopping 23.6 hp loss)

factor in effective change due to the junk we drag around (say 50lbs - you'd be surprised how easy that is) = 209 hp

factor in octane drop running 91 instead of 93 (like here in california) = 205 hp

don't get me started on the effect of heavy wheels, tires, and big brakes

it's no wonder we have hyundais passing us

you can see that, while weight and fuel play a part, the largest loss is in condition of the engine - keep the compression up and keep your power - relative to things you would do to your car for power, obviously this is one of the most expensive propositions, but all the bolt on tweaks in the world (chips and such) won't make as big of a difference as a valve job<!--QuoteEnd--><!--QuoteEEnd-->

Flash,
I've been thinking about exactly this issue as I contemplate my next mod.
Is it more cost effective to do a valve job / new head, or go to RSB stage 2 and exhaust mod?
Since my car just passed 140K miles, I'm guessing it may be the former.
I just haven't done the math yet...or the compression test.

The RSB web site shows a reconditioned cylinder head and the header both at about $1K.

Any guesses?
Jamie

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[flash]

at 140k, assuming your compression numbers are down, i would do the valve job - ask pete if he did a test and what the numbers were

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[PorscheDude]

I had a valve job and the head reconditioned at 138k,
and it made a huge difference.

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[rhudeboye]

good point. Regaining the power that supposed to be there is a very logical move. Just not a cheap one. So much easier to spend a little here and a little there for chips, exhausts and plugs and such.

I was surprised however that when Dan had his done he wasn't really blown away at the results.

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[flash]

another thing to think about is the effect of bolt-on stuff relative to the condition of the engine

chips and such are tuned to a perfect engine - they add timing and fuel (varying from chip to chip) based on the needs of a tight engine - a tired engine can easily receive too much of one or the other and end up running WORSE

even if you do get gains from some things, they almost always are proportionate to the condition, so you will see larger gains with a tight engine than you will with a soggy one

while these engines are capable of running 200k or more, they won't do that at full power, an it won't do that without some serious service - it will be reducing in power as the miles go up, unless you do things to freshen it up - people with high miles will tell you "it runs fine", but if you compared it to a fresh engine, the story will be very different - there is a big difference between "running" and "running strong"

also, the head gaskets are deteriorating - this is a function of age - this will also begin to lower compression, and thereby lower power - running the engine harder with an old head gasket also increases the likelihood of blowing it

the same can be said of running a tired engine harder with bolt on performance components - if you are running rich as a result of them, this will increase the friction and wear due to fuel wash and increased heat

the bottom line is that there is no free lunch, our cars are old, and our engines are mostly tired - freshen them up if you want to have the kind fun that these cars can be

as for dan's car, i'm not sure what is going on there - i didn't get to do before and after tests, or see where the cam timing was and is now, so i can't speculate on that - there are enough variables at play that he could easily have fallen into both ends of the spectrum

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[rhudeboye]

<!--quoteo(post=81671:date=Oct 12 2009, 09:56 AM:name=flash)-->QUOTE (flash @ Oct 12 2009, 09:56 AM) <{POST_SNAPBACK}><!--quotec-->it's no wonder we have hyundais passing us<!--QuoteEnd--><!--QuoteEEnd-->

That was hyperbole right? I still feel that no N/A inline 4 is going to take a 968 w/o some serious turbo work done to it.

Drove the 68 into work today seeing as how the roads were pretty clear (Federal holiday). Had a newer Civic Si with a few mods and some Recaro seats run up on me. We got a clearing and I buried the pedal with the car in 5th rolling around 75. I was a bit worried as he stayed there for about 2-3 secs. Then he started to fade. As I held it down he drew further and further back. I backed off as we were back in a pocket of traffic, he comes back up gets around me, w/ some wreckless driving, and at the next opening He floors it and I follow, this time I drop into 4rth gear. I ran up on his bumper with every flex of the right foot. Simply no competition.

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[flash]

lol - no hyperbole - there are hyundais with well over 300hp now - scary stuff

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[ds968]

<!--quoteo(post=81694:date=Oct 12 2009, 11:54 AM:name=rhudeboye)-->QUOTE (rhudeboye @ Oct 12 2009, 11:54 AM) <{POST_SNAPBACK}><!--quotec-->I was surprised however that when Dan had his done he wasn't really blown away at the results.<!--QuoteEnd--><!--QuoteEEnd-->


Don't read too much into that, I simply cannot be relied upon for any valid seat of the pants feedback - just as an example, most owners who had the strut tower and the lower braces installed raved about a complete transformation of the ride, I on the other hand cannot detect any difference at all in the before and after feel, the ride, the handling, etc. I honestly don't think I could tell if my car had 10% more HP or 10% less HP or torque than it did before. It was very fast before, it's very fast now, but just feels like a different fast - not sure how to explain it.

So don't let my poor excuse for a butt-o-meter [img]style_emoticons/<#EMO_DIR#>/rolleyes.gif[/img] influence anyone's decision to do valve job; if you're looking for a new surge of fresh power there is no doubt the job will deliver that, whether I'm able to feel it or not..

I was also contemplating expanding to a 3.2 L concurrent with the head job, just could not justify another $ 4K or
$ 5k expense on top of what was already a decent chunk of change.. particularly if the end result would not have have brought about that "blown away" impression either..

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[Cloud9...68]

The depressing thing about this is the extreme slipperiness of the slope here. Unfortunately, the two weak points of this engine appear to be at its opposite ends - the head (valve guides, seats, and gasket), and the rod bearings. Neither of these are cheap or simple to repair/replace, and by the time you go to the trouble of taking care of them, why not do the rings, too? Pretty soon, you're talking about a complete rebuild.

I'm not really sure what to make of this situation. But given the fact that my butt-o-meter is no better calibrated than DS968's, my inclination is to drive it until it starts displaying some scary symptoms, then tear it all apart, and run the best oil available for the next 100K+ miles.

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[flash]

perhaps not the worst course - a tough call indeed

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[PorscheDude]

Rod bearings are actually pretty easy to R&R if there is no damage to the crank.
The parts including seals, bearings, oil pickup and rod nuts is less than $400.

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[Darryl]

<!--quoteo(post=81725:date=Oct 12 2009, 08:00 PM:name=Cloud9...68)-->QUOTE (Cloud9...68 @ Oct 12 2009, 08:00 PM) <{POST_SNAPBACK}><!--quotec-->The depressing thing about this is the extreme slipperiness of the slope here. Unfortunately, the two weak points of this engine appear to be at its opposite ends - the head (valve guides, seats, and gasket), and the rod bearings. Neither of these are cheap or simple to repair/replace, and by the time you go to the trouble of taking care of them, why not do the rings, too? Pretty soon, you're talking about a complete rebuild.

I'm not really sure what to make of this situation. But given the fact that my butt-o-meter is no better calibrated than DS968's, my inclination is to drive it until it starts displaying some scary symptoms, then tear it all apart, and run the best oil available for the next 100K+ miles.<!--QuoteEnd--><!--QuoteEEnd-->


+1 here...as long as I have no major mechanical failures, I say run until it needs fixing and then fix it all, that is, of course, you continue to do any and all necessary preventative stuff along the way. If you're concerned, you can always do regular compression and leak down tests to see how far gone you are and the compare the rate of decline of performance with the checking account balance to determine when to "get 'er done".

- Darryl

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[flash]

yeah - it all comes down to how low you are willing to go

in my case, i'm barely tolerant of what i have with compression near perfect and all the bells and whistles - any less and i'd be losing my mind

the main point i was trying to make is that all the bolt on goodies out there barely add the amount of power at full compression as going from a weak 185lbs to a like-new 200lbs of compression does, and they add even less at the lower compression, and could even do harm if things get too bad and you have the wrong stuff

a lot of engines have even less compression out there, so you can just imagine what that would be like

so, if you're sitting on 80k or more, get a compression check (and a leak down too if you can) and see where you are - odds are you can forget about saving up for that cat-back and focus on a valve job - it's not sexy, but it makes a bigger difference

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[Scott Collins]

<!--quoteo(post=81720:date=Oct 12 2009, 04:15 PM:name=flash)-->QUOTE (flash @ Oct 12 2009, 04:15 PM) <{POST_SNAPBACK}><!--quotec-->lol - no hyperbole - there are hyundais with well over 300hp now - scary stuff<!--QuoteEnd--><!--QuoteEEnd-->

Anyone remember the story of the Hyndai driver getting two tickets on the same day for doing something in excess of 140mph on a California freeway? Speed camera got him twice if I recall, coming and going.

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[rhudeboye]

<!--quoteo(post=81741:date=Oct 13 2009, 07:18 AM:name=Scott Collins)-->QUOTE (Scott Collins @ Oct 13 2009, 07:18 AM) <{POST_SNAPBACK}><!--quotec-->Anyone remember the story of the Hyndai driver getting two tickets on the same day for doing something in excess of 140mph on a California freeway? Speed camera got him twice if I recall, coming and going.<!--QuoteEnd--><!--QuoteEEnd-->

I do, that was in C&D, or was it motor trend.

I remember the argument was that the car, which was a rental, wasn't capable of reaching 140. They go it out in the open and ran it full throttle, it took a while but it made it to 140. Either way, that was a 4 banger and in no way could that out run a 968. I think that has like 170HP

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[flash]

yeah - they've got a lot more power now - even the V6 genesis has 306hp and 266 ft/lb

my point though was that nearly everything now has the power we had when our car was new - most generic cars have performance specs near or better than ours - without getting into any "yeah but......" conversations, the entire focus of the thread was to illustrate that we often overlook the impact of letting an engine get soggy, and instead focus on items that won't make as much of an impact as freshening up the head

rule 1 of modding an engine is to always start with a perfect running one - you wouldn't go out and run a marathon without first getting into shape - you'd break down very early - your car is no different

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[rxter]

OK OK I'm in. Saving up as we speak. Now if I just had a mechanic that I trusted......

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[flash]

lol - working on it

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[Cloud9...68]

<!--quoteo(post=81727:date=Oct 12 2009, 08:11 PM:name=PorscheDude)-->QUOTE (PorscheDude @ Oct 12 2009, 08:11 PM) <{POST_SNAPBACK}><!--quotec-->Rod bearings are actually pretty easy to R&R if there is no damage to the crank.
The parts including seals, bearings, oil pickup and rod nuts is less than $400.<!--QuoteEnd--><!--QuoteEEnd-->
Wow, your definition of "easy" is a bit different from mine. I think you get to keep to paint on to replace these things, but pretty much everything else comes off. And as far as the cost, it's that slippery slope thing again. As long as you have the pan off, you might as well spring for the $300 windage tray, right? And then there's the obligatory wheel alignment - ka-ching - another $200 - $600, depending how extensive you want to get (corner balancing and the like). And after going through 16 hours of hard labor (which is what it would take me, given my experience changing my motor mounts), it seems prudent to install the removable cross-brace (about $400, including shipping) to make the next bearing replacement a whole bunch easier. So, yes, you could conceivably get by with about $400, but the task could quickly balloon to close to $2K, if you include all the bells and whistles.

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