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im not that well learned in actual engine operation, i mean the physics of it all. So, we all know that d17s dont respond well to mods, we all complain about it, but why does it happen. What did honda do to it to make it this way, say comapred to the b series? it is in the ecu? the engine measurements? just curious...

thanks!!!

 
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it is a sohc compared to a dohc............ vtec

also, gsr heads flow pretty damn well from factory......no need to port them.

 
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Well, if an engine is designed by an engineer who knows what they're doing then their finished product will be as efficient as possible. Optimum intake pressure and exhaust pressure will be taken into account when designing the air flow properties of the head. Therefore, the only way you're going to make any significant improvements is to completely change the dynamics of the engine. The d17 could make much more power, but it would involve significant work to the internals (i.e. increasing bore, increasing compression, etc.). Of course you could always make more power by creating a turbo motor, but that would cost Honda an incredible amount of money in development costs. The Civic is intended to be the most efficient and economical compact on the market. That wouldn't be true if it ended up costing $20K for a DX and only got 20 mpg.

 
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its a 1.7 l engine.......101 cu. in... and its pumpin 127 horse to the crank (ex)....thats pretty good if u really think about it. its so small and is already high performance.

 
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I am gonna have to agree with hotrod...Although we dont put out a ton of hp, it is plenty to get you moving. For 1.7 liters, the engine gets the job done and it does it very well. The only thing I hate about the engine is, like stated earlier, bolt ons dont do anything. That would be the one thing I would change and I am planning on doing a swap in a few months.

 
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you ppl are not reading the post correctly. He wants to know why our D series motors do not respond to mods like B series motors. You talk about only being a 1.7L.......what about B16's.......they are smaller.

Flowerpower........read my post.

 
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an efficient engine is considered any engine making at least 1hp per cubic inch of displacement or 61.02 hp per liter or 61.02 hp per 1000 cc
this is for n/a engines mostly
the s2000 and integra type r motors are more efficient in this sense than a 250grand porsche gt

 
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the D series engine is the most basic engine from Honda..... for basic use, basic transport. B16 series was built for high revs and less efficiency..... but just b/c B16 is smaller doesnt mean anything (ie. F20C). B16 has more revs, probably higher lift on the valves.... ecu should be very different.......

 
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thanx, u are the only one that understands my original question. so, if i got the head ported, and when i get internals, opt for the oversize? then the engine would be more responsive cause it wouldnt really be the D17 that honda made. what im trying to get at is that, could you make the d17 have the same flow rates and such like a more receptive honda engine, ex b and k series?

sorry, i really am having a hard time writing this while making sense, the question is a clear as day in my mind but when typing it all falls apart. but i think you know what im trying to say...

 
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btw, the k20 2.0 makes 100hp per liter, and the older b16 1.6 made 100hp per liter. the d17 is not at the height of performance in any means, but we have established that it is not created for performance but economy.

the d17 should be making 170hp to be the same as those and were not even close to that

 
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IMO going all motor on a sohc is a waste of money. Some ppl will argue that, but i have yet to see someone make over 200whp all motor on a streetable sohc. If you understand vtec and lift they you will understand how dohc motors make more power.

The way to make power on our motors is by porting the head to increase air flow, and doing a cam regrind. Also, the biggest way to make power is to install higher compression pistons. Wanna go crazier........bore the TB and get a aftermarket IM. Since none is available for our cars, get one custom made/fitted.

Price of all this..............about $4,000. The gains.........mabe 25-30 whp. Not really worth it IMO. You want more hp......slap on a 50 shot of n2o and call it a day. Way cheaper and more practical. The only real way to make power on sohc motors is through F/I.

 
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keep in mind both of those are DOHC ours obviously isnt

 
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The engine was designed as a low revving emissions motor. Small ports for torque, not high revving HP. All the bolt on mods are aimed at changing the characteristics of the motor into a high revving one because thats how you make power. But doing this means that if you dont change all the important airflow & tuning components then the thing does not work well with itself and little, if any gain is realized.

I'm going to cheat and repost a thing I did a couple of months ago on another thread:

It's all about air flow, more air flow into the cylinder = more power.

Throttle Body: simply one of the smallest I have ever seen
Intake Manifold: plastic & almost un-moddable. Good for low speed torque, not good for HP.
Head: ungodly, requires MAJOR reworking of the ports, it's very restrictive. again good for torque, not HP
Cam: just another emissions cam, VTEC or no VTEC
Exhaust manifold: Runners so small that you just cant believe it, again, good for velocity & torque, not HP
Exhaust: small as well. see above.

The main thing is to get air through the system. So simply changing out a throttle body to a huge one will not make any more air go through, it's still restricted by everything else. The motor is reliable and with a good CAI, throttle body, manifold, cam, P&P head, header & exhaust, very good gains can be made. But, if you don't do all of these, then you will only see very small gains.

When I was selecting an engine to use as a base for my bonneville buildup, I wanted to stay with the D17, it would have been soooo much easier than doing a whole swap. I talked to a very reputable drag import engine builder and tried to talk him into recommending the D17. Even with all the money I would save from not having to do a swap and redirecting that money into the D17 he said the following:

"I have never seen a D15/16/17 head flow over 200cfm. Ever. No matter the budget". Then I asked how a B series would do and he said with his standard port & polish, I should expect about 290 cfm. Thats almost 50% more flow (power potential). btw, K series = 320 cfm. Thats why the D17, in it's current form will never be a player in the high end Honda racing scene. It can be made into a decent street runner, you just have to upgrade it as part of an entire package, not piecemeal. Understand that each part removes a restriction, but that the ultimate gain cannot be realized untill all the restrictions are removed. With that in mind, pay close attention to mfg test results and the level of mods on the test car, as it will influence the HP gains they got. Imagine someone who does every mod listed above and then puts the stock throttle body back on. It would KILL 95% of the power that was gained. They dyno it, and then put on their 75mm TB and pick up all the power that the engine used to have. Then they claim the TB was responsible for ALL the power gain!

Just my $0.02

 
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best explanation I have seen to date.

 
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[QUOTE=djmota]best explanation I have seen to date.



i agree

 
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you are right. i retract my point.

 
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Mercedes uses SOHC engines. Take, for example, the CLK430. 4.3L V8, high horsepower, high torque, SOHC. I don't know about the efficiency of the engine, but I do know that it is SOHC.

 
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true, but there is a big difference from 1.7 4 banger to a 4.3 V8.

 
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this thread is over my head

 
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good point I have a 1969 vw bug the stock engine put out about 40 HP, and wasn't dog slow, I spent about $3,000.00 on a 1915 or 1.9 Liter engine straight cut gears high lift cam, 1.25 ratio rockers, chromolly pushrods, dual weber 40 carburetors, and all it is really fast now, but probably only puts out around 80 horse power max. and its about 250 CC larger than our vics engines.

Volumetric Efficiency that's all I can say about that. Oh by the way that engine is brand new, but the technology and the design is like 1936 era design.