I'm trying to build a NA B16a to 180-200 WHP. I'm getting about 42 Highway MPG with my mildly modified B16a YS1 with LS 5th. I want to keep that milage, but still reach my 180 WHP goal.

Crower Sells these Cams:
http://www.crower.com/cat/impo...shtml
63402A-2

They are Stage 2 Cams with Stock Idle Lobs. It's my understanding the Idle Lob profile determines small part in good gas milage(helps keep good TQ at low RPM). What kind of effects will I get if I get even milder Idle Lob(milder than stock) and have very radical Stage 2 VTEC lobs? Positives and negatives about this are appriciated!

 

Bump for any ideas

 

I have these cams for sale, so if you decide this is the route you want to take shoot me a PM.

 

Well, first off it is not a bad idea, but I think that the expense of custom cams may off-set the money you save through better mileage.

Second, the compression needed to make 200whp on your b16 might cause you probelms as your dynamic compression on the low cam would be significantly higher than when on the high cam. This could lead to detonation. That's bad.

Third, your torque curve might get really messed up right around VTEC. If you have a really agressive lobe that has a high rpm torque peak and a mild lobe with a real low torque peak the two curves may not intersect very well and that could negatively affect daily (spirited) driving. It might not be too bad if you only drag race and are only concerned with the top 2000 rpm.

My 2¢,
Pirate

 

don't the cam profiles sort of have to overlap?

i think that Honda went for the same thing with the new iVTEC on the K series. the problem was that for the RSX-S/DC5R to make the power that we all wanted, they had to sacrifice the fuel econ available with the base RSX. also, most everyone who builds higher performance K series engines deletes the 'i'; the variable cam phasing, since wilder cams (with more lift and duration) cannot tolerate much active phasing (like adjusting cam gears on-the-fly), especially with larger valves.

removing the stock cat can actually help improve fuel econ, since the stock ecu runs the engine in a lean-rich cycle to heat and cool the cat. without a cat you have less restriction/pumping loss for the engine, as well as being able to run in a steadily leaner state at lighter driving loads without having to worry about burning out your cat. you can run the renault turbo diesel cat, which Hytech sells. it's the stocker for some Ferraris, McLaren F1, etc. since it's made for diesel, you can run it hot/lean all of the time, and it will last. also, if you get, say, a 3" version, you'll eliminate much of the restriction of having a cat; it flows pretty well.

much of the inefficiency of an internal combustion engine comes from throttling, pumping losses, and attendant friction. note that while fuel consumption for daily driving on force-induced engines is typically higher than on NA versions of equal displacement, FI is great for fuel econ at lower loads and lower rpm, e.g. highway driving, since the positive intake manifold pressure (PIMP) allows the engine to breath much more easily at lower throttle positions; the engine no longer has to suck so hard on the intake stroke to pull the air past the throttle and valves; the pressure provided by the turbo or supercharger pushes it right past. there are, of course, pumping losses of driving either one, but if they are setup properly (good manifolding, cams, and tuning), they can provide superior performance and fuel econ to NA, especially for highway use. just something to consider.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PirateMcFred &raquo;</TD></TR><TR><TD CLASS="quote">Well, first off it is not a bad idea, but I think that the expense of custom cams may off-set the money you save through better mileage.
</TD></TR></TABLE>

Crower sells that type of cam for $535, and I need cams anyways, so it might not be too bad. a custom ground set is $750 or somthing. With gas prices these days, a proprietary set custom grinds for Gas/Peformance might be in high demand soon!

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PirateMcFred &raquo;</TD></TR><TR><TD CLASS="quote"> Second, the compression needed to make 200whp on your b16 might cause you probelms as your dynamic compression on the low cam would be significantly higher than when on the high cam. This could lead to detonation. That's bad.</TD></TR></TABLE>

That's another concern of mine. How much compression should I use before I really have to richen the fuel to where my economy will be toast? I know Honda runs High compression in their HX model(10.9:1) for better effeciency.

What Gas economy would be lost if I retard the ignition a bit to prevent detonation with higher compression?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PirateMcFred &raquo;</TD></TR><TR><TD CLASS="quote">Third, your torque curve might get really messed up right around VTEC. If you have a really agressive lobe that has a high rpm torque peak and a mild lobe with a real low torque peak the two curves may not intersect very well and that could negatively affect daily (spirited) driving. It might not be too bad if you only drag race and are only concerned with the top 2000 rpm.</TD></TR></TABLE>

The transition and change in air flow can really effect the VTEC transition. If I'm on the track, this would only effect my 1st gear. I could change my launch control to start in VTEC, thus my track time would never see the Idle Lobs. Good or bad?

I know for Daily driver, that transition could screw me up. If I'm passing on the freeway, I'll drop a gear to be in VTEC already, so my transition won't mess me up. Does the transition really have that dramatic, undesired effect? It might even feel cool, slowing down a bit, then a swift kick in the *** when the cams really kick in.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slofu &raquo;</TD></TR><TR><TD CLASS="quote">don't the cam profiles sort of have to overlap?

i think that Honda went for the same thing with the new iVTEC on the K series. the problem was that for the RSX-S/DC5R to make the power that we all wanted, they had to sacrifice the fuel econ available with the base RSX. also, most everyone who builds higher performance K series engines deletes the 'i'; the variable cam phasing, since wilder cams (with more lift and duration) cannot tolerate much active phasing (like adjusting cam gears on-the-fly), especially with larger valves. </TD></TR></TABLE>

That's what I kind of understand about the RSX-S iVtec valve train. A Tuned RSX-S will have an absolutly flat TQ from about 2000 RPM to +8000RPM. The VTEC transition feels non-existant. It's an engineers dream come true! I don't know much about Fuel econ physics involving that cam phasing, but from what I can guess, if you had the right cams, you 'could' get better milage and only suffer a bit from the transition. For me, I'd suffer the slight peformance loss to get much better fuel econ. However, people get an RSX-S for POWER not as much for fuel econ.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slofu &raquo;</TD></TR><TR><TD CLASS="quote">
removing the stock cat can actually help improve fuel econ, since the stock ecu runs the engine in a lean-rich cycle to heat and cool the cat. without a cat you have less restriction/pumping loss for the engine, as well as being able to run in a steadily leaner state at lighter driving loads without having to worry about burning out your cat. you can run the renault turbo diesel cat, which Hytech sells. it's the stocker for some Ferraris, McLaren F1, etc. since it's made for diesel, you can run it hot/lean all of the time, and it will last. also, if you get, say, a 3" version, you'll eliminate much of the restriction of having a cat; it flows pretty well. </TD></TR></TABLE>

I'm running a test pipe with slight muffling. My car is also registered in Tri-Cities, WA where there are no emission test! I'll look into that diesel cat idea though.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slofu &raquo;</TD></TR><TR><TD CLASS="quote">much of the inefficiency of an internal combustion engine comes from throttling, pumping losses, and attendant friction. note that while fuel consumption for daily driving on force-induced engines is typically higher than on NA versions of equal displacement, FI is great for fuel econ at lower loads and lower rpm, e.g. highway driving, since the positive intake manifold pressure (PIMP) allows the engine to breath much more easily at lower throttle positions; the engine no longer has to suck so hard on the intake stroke to pull the air past the throttle and valves; the pressure provided by the turbo or supercharger pushes it right past. there are, of course, pumping losses of driving either one, but if they are setup properly (good manifolding, cams, and tuning), they can provide superior performance and fuel econ to NA, especially for highway use. just something to consider. </TD></TR></TABLE>

I agree that turbo charging is the provides the best power to fuel economy ratio. I've even thought about taking Honda's DOHC ZC and destroking it to a 1.5 and turboing that. The R/S ratio would be similr to a GSR and the DOHC will allow me to rev it without valvetrain problems. I can get mega power with revving it and maintain good fuel econ from the 1.5l Or the same idea but with a mini-me 1.5 or the D15Z. You wouldn't be able to revv the **** out of it, but definitly revv the **** out of it.

 

You can have larger primaries and better gas mileage at the same time. Those two things are not mutually exclusive.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Rocket &raquo;</TD></TR><TR><TD CLASS="quote">You can have larger primaries and better gas mileage at the same time. Those two things are not mutually exclusive. </TD></TR></TABLE>

Ok, you got my attention, can you elobrate some? I know a milder cam will produce better Low RPM TQ, so I don't have to shift at higher RPM. I'm open to any ideas!

 

From what I've seen with our non-vtec cams and BVTEC primaries you can get 30+ mpg with profiles from 205 - 225 duration measured at @0.050.

On the BVTEC cams where we provide the maps I run 40+ degrees timing in the cruising portion of the maps and that works killer.

Smaller profiles like stock with 180 to 190 duration choke off the motor where we spend most of our time crusing. 3,500 to 5,000 rpms on the highway.

 

So your saying that the engine runs ineffecient while Cruising between 3500-5000 on highway? Something similar to pump loss. With a slightly better, more aggressive profile the engine can run more effecient on freeway?

I did a 94 LS 5th gear swap(.714:1 ratio). At 70, I'm at 3000 RPM. What would be best for that setup? I'm thinking stock.. maybe.

 

I think that's what's going on.

A profile with 205 duration will be real good at 3k rpms.

 

I think I'm running 37-38° advance, stock P30. Do you know if changing the Lamda tables effect closed loop driving A/F ratio? I set all mine to 1.00 or 14.7 from 500-4000 and up to 403 Mbar or 17 vacuum. Do you know what Mbar you are crusing at on the Highway @3500 RPM with your 205 duration cams?

 

On level road cruising, depending upon the aero of your car you'll be around the 4 - 5th columns. You should always try to achieve lamdba = 1 if you are running closed looped with a narrow band 02 sensor.

 

Thanks for the info. I've been searching all around, but none seem to explain the effectiveness of the Lamda table.