Team-BHP - "Dude I bolted on 25 BHP" FAQ !!

Quote:

Originally Posted by rdkarthik (Post 416755)

say from 1000 rpm right upto 8000 rpm? Is it like fuel flow (from the main jet? ) remains the same (max flow) the entire range ?

Isnt that what the tapered needle is for? (atleast on bikes)
Keeping the ratio roughly the same but proportionally increasing the jet opening with the opening of the throttle...

cya
R

Quote:

Originally Posted by Sideways (Post 416760)

Ya but you need the EGR to be there unlike the breather connection to the air intake which can be disconnectd cause it does not matter if you disconnect it. It's like an appendix operation. Organ doesnt do too much but can cause a whole lotta trouble.

EGR you need to keep there cause it keeps combustion temps down. So it's a necessary evil.

And by re routing the breather, imagine, no more sticky dirty fouled up throttle bodies, fouled sensors etc. Plus you also avoid hot air from inside the engine from going into the intake. I am sure there will be some gains, not too much though.

:thumbs up yes sir ..
but the function of the EGR is to lower temperature in order to reduce emissions (Nox emissions)
Disconnecting it would cause [1]high emissions + [2]engine knock due to high temperatures.
we dont mind [1]"high emissions", but the [2]"engine knock" just curious what if we again possibly tune the engine after disconnecting the EGR ? can we do that ?

Quote:

Originally Posted by Sideways (Post 416773)

And just another question - Why have you guys ruled out lightened flywheels ? Please understand that cetain mods work well in a package.

no we haven't ruled them out completely.
we just said it will be good for certain applications. its a good mod but in a stock car in city conditions it may not be that great...e.g if we just bolton a lightweight flywheel only and expect great stuff to happen.

Quote:

Originally Posted by Sideways (Post 416773)

A lightened flywheel in combination with a short (close ratio) gearbox will be a superb mod.

:thumbs up agreed 100%

Quote:

Originally Posted by rdkarthik (Post 416755)

But i would like to know, what happens when i am at full throttle, say from 1000 rpm right upto 8000 rpm? Is it like fuel flow (from the main jet? ) remains the same (max flow) the entire range ?

theoretically i dont know enough to answer that question. i guess a larger jet is required because jets flow based on the vacuum signal, which is altered when you improve the VE.

Let me tell you how we re-jet ("we" is in the literal sense, i dont know how others do it).

First we start with the venturi. Make sure we have the venturi size just large enough that it sputters and stumbles the least when we go to WOT at low rpm ( similar to the situation you described).

Then we select the main jet size and make it run right at the top end.

Then the right emulsion tube to check mid-range response.

Then the air-corrector to check part throttle response.

Lastly the idle jet to get it to idle properly. Off-idle response is also affected by air-corrector and idle jet.

I am talking about constant venturi Solex and Weber DCOE carbs. For variable venturi (SUs and motorcycle carbs) it is quite simple (actually tough sometimes) matter of changing needles instead of air-corrector and emulsion tube.

No wonder people prefer fuel-injection. All this is hit-and-miss, and require fair amount of experience and "intuition", with the DCOE's being extremely tough to get right, specially if you are running two of them.

Quote:

Originally Posted by chetanhanda (Post 416778)

hey sideways, some more thoughts from my side..
.. EGR isnt open all the time , so the engine wont mind if its closed during certain conditions only.If it gets stuck open it creates issues..wouldn't it be good to block this along with the PCV as u suggested ? there are EGR block plates sold for this purpose.

blocking the EGR and PCV may (a) help to keep the intake slightly cooler becoz its not circulating hot exhaust gas back in (whenver the EGR is open) (b)Keeping intake cleaner from exhaust gasses

Quote:

Originally Posted by Sideways (Post 416760)

I am sure there will be some gains, not too much though.

yes,possibly, lets see if the guys have any articles/dyno readouts abt EGR and PCV blocking ?
plz add to this..

@anathkamath - I am a little confused here.. Supposing i was at full throttle at low rpms, airflow through the venturi would be low as well, that means a lower vacuum, hence a lower amount if fuel is sucked out of the main jets, at higher rpms, airflow will be high contributing to higher vacuum at venturi sucking out more fuel from the main jets.. This is the way i guess it retains the required approx afr throughout the operating range....

When you say the main jets flowed at max all the time, i guess you mean max flow with respect to pressure diff in atmosphereic to venturi, which is logical as thats the only way it can hold the approx afrs.. Pls correct me if i am wrong here... This also means by increasing airflow you effecitively increase fuel flow as well, limited to the max flowing capability of the jet ( self correcting to increased airflow to an extent ) .. But if you meant fuel flow from main jets is max ALL the time, it is just not possible to retain operating afrs through the rev range.......

This may help, its off the edelbrock carb manual -
"The fuel flow rate in the Main System is proportional to the air flow rate; as air flow increases - from either an increase in throttle opening or an increase in engine speed at the same throttle opening - the fuel flow also increases by nearly the same degree. "

EPS Carb Manual: Section 1 Theory of Operation

btw my 100th post :)

More than the gains, my intention was to avoid the fouling of the throttle body and the Plenum.

Chetan, with regards to PCV, we aren't blocking it, we we wre only re routing. In effect there is no harm being caused. But with respect to EGR you are talking of completely blocking it off. I will have to research a little more before I can comment. Until then i would avoid doing anything with the EGR.

If the positive effect of the EGR is to cool down the combustion temperature, maybe we should try and find a way of providing cleaner air for this purpose.

Quote:

Originally Posted by Sideways (Post 416897)

EGR simply works by displacing useful air by inert exhaust gas, effectively bringing down comustion temps. Primiarly used to reduce NOx emissions. If you provide clean fresh air, its like opening throttle a little more, you will not reduce combustion temps....

EGR is most of the times used for part throttle conditions, and can be safely disconnected, provided there is no interference with the ECU.

Quote:

Originally Posted by chetanhanda (Post 416765)

I mean the OHC, becoz my USDM civic = OHC in India
I know CIVIC is diff from OHC in india, I have an OHC in India

Ok I am no expert here but one correction. AFAIK, the USDM civic is not the same as the OHC(old Honda City) in India.

We have the new 8th gen Civic here in India and the 6th/7th gen was never sold here as the City. The OHC in an Asia specific model.

Quote:

Originally Posted by ananthkamath (Post 416862)

i'm being a prick here, but for the damage it does to the environment, I dont think its worth the miniscule extra power. Same goes for removing the cat. I dont think the gains are sufficient enough to warrant removing it.

haha .. I dont mind being a prick also for a few extra bhp or for a cleaner intake plenum.
you may be right abt damage to environment Vs power gains to be had.
luckily there maybe only a few handful creeps like us to go and reroute the EGR/PCV..

Quote:

Originally Posted by vid6639 (Post 416916)

relax vid6639 ,just hold on. Im not a newbie here but thanks for the inputs. Im quite aware of the civic JDM and USDM generations of civic.

You are not getting my point here, just let me give you a background what the confusion is:

I have OHC in India which will be called as a civic in the US.
I also have a civic coupe in US and there is no such thing as a D15/D16 "city" here in US so I keep referring to my OHC in India by mistake as a civic.
I've so got used to calling my OHC as civic..which creates confusion becoz in india the Civic is diff from City.
Also JDM and USDM D15 and D16 are called as civics.
Its just that in India old civics are called OHC and new civics are called Civic.

Quote:

Originally Posted by vid6639 (Post 416916)

The OHC in an Asia specific model.

Yes but everyone here in US calls it the "old civic" or the "asian civic"... and its not a totally different model from the civic anyway, its based totally on the civic.

Quote:

Originally Posted by rdkarthik (Post 416909)

EGR is most of the times used for part throttle conditions, and can be safely disconnected, provided there is no interference with the ECU.

yes ..right, its not open all the time.

Quote:

Originally Posted by chetanhanda (Post 416855)

.. EGR isnt open all the time , so the engine wont mind if its closed during certain conditions only.

I've seen some EGR blocking plates/parts being sold in aftermarket to prevent it from entering the intake so maybe they really dont affect the ECU in some cases where they dont have EGR position sensors etc.

Theres big difference in geometry of OHC Chasis & a civic chasis in terms of lower arm & suspension components,Civic chasis is far far stronger than OHC no way it can be compared with OHC Chasis,
the chasis in civic can be removed from subframe since its bolted on but in OHC its integrated,not to mention about handling of Civics compared to OHC.
It will be better if civics are not compared with OHC & i am not talking about engines here.

Quote:

Originally Posted by Ford Rocam (Post 417508)

It will be better if civics are not compared with OHC & i am not talking about engines here.

Im talking about D15 and D16 engines here.
Because we were discussing the power gains to be had with a header in a D16(old gen civic) and if the same should be expected in a D15 (OHC)

So if its the suspension which you have pointed out, you may be right abt that, i wouldn't argue on that.
But I had posted this earlier in context of the headers on d15/D16 and gains on the dyno.