Head Flow and Big Cams

[mdb4879]

Lol, I'm 20 and I remember watching both of those shows as a kid. Especially Thundercats. That was one of my favorites. But I'm really more in the DBZ generation. Nothing beats DBZ... nothing.

Oh how I could go on a long tangent about the E-series. If we had an E-series forum I'd be the head guru, lol.

I wouldn't exactly call the E16 a power monkey, though. It was really just an econobox. I guess they did have some potential, but man did you have to work for it. Then again I guess back in the day Rebello Racing getting 225hp (probably around 150lbs/tq as well) and revving to 8800rpm with an 8-valve, SOHC, 1.6L with an 88mm stroke was (and still is) quite a feat. From the factory they had a lot of restriction (I can go into detail if anyone would care to start a lesson/discussion on oldschool Nissan and we can change the thread name). But I just love how simplistic and easy they are to work on. And they leave so much room in the engine bay. For those of you who think a CA is small, you should see an E16 next to it. The CA will look like an SR, lol.

Sadly that motor didn't go in the car like that. The TBI manifold went on it and it was just a stocker with DIY mods as it was just suppose to be a car I could drive forever. I have all the top end stuff to make about a 150hp E16 I'm pretty sure if I had a bottom end for it. But much like Dee I discovered the CA and now that project is on the farthest in the back burner. The carbs do make a nice ornament for the man cave

[mdb4879]

Hondas don't really run much more compression relatively. Static compression, yes, but dynamic compression, I doubt it. Because of their long duration the cams bleed off a lot of the compression. Plus I'm sure you're referring to a stock bottom end boosted Honda. Typically the "built" ones drop the compression to 9.0:1 and some as high as 10:1. Whether the compression really makes any more power is debateable because with the higher compression comes a lower knock threshold. Timing is retarded and peak cylinder pressure is actually roughly the same (same torque). Off boost I'm sure it's more responsive. Same principle applies to all-motor, just different compression.

Relative to the line of being overcammed and undercammed in terms of compression we all run the same figures. The actual values may vary between the motors, but relative to having too much or too little compression we are the same. They may run a little more compression, I'm not sure. But mostly they make the power they do because of synergy and how well everything flows. Even with some of their really big ported heads flow is increased across the entire rev range, not just up top. It seems only in extreme porting is there actually any sacrifice in bottom end. But for the most part with a good head job gains will be seen everywhere. Similar to adding displacement except that the powerband doesn't shift downward and can actually relieve some restriction in the upper rpms.

My thinking was that this still applies in boosted motors and that with a really good head there would be more flow everywhere. So faster spool and at a lower rpm, and more air flow/power at lower boost levels. And I"m not even talking about revving the piss out of a CA anymore, I'm talking about more torque across the board.

[dash]

Some club4ag members 11000 rpm 4AGs were no quicker than their 8000 rpm counterparts. Definitely far more unreliable tho
don't see the purpose revving the piss out of any boosted motor. A "pump" will only be more efficient in a specific range
CA already proven a "good (enough)" head. Lotsa builds posted featuring "more torque across the board". Its in the combination of parts and the tune
I never see this 'great head flow/bigger cam' translating into "faster spool, more tq, quicker car" etc....
Peak hp maybe, if that's your thing

"Street" VW bettle ran 9s from the early 80s. Turbo sucking thru 4 bbl holley carb. No efi, no intercooler, no spray, no 'great honda head'.

[boost_boy]

For those that want the faster/earlier spool from the CA18 may want to look at roots type supercharger with some aggressive tuning under 5000rpm. Or one may want to use a smaller, but more efficient turbcharger. like m y old t2/t3 hybrids I use to have custom made from my turbo provider. You guys buying the bigger SR turbos, that .86 hotside is your achilles heel. Sure you'll get a little more power just above midway through the rpm, but you are gong to lag as well in the lower rpms. As for the CA's head, it flows enough for what most of you require.

[Liquid_Neon]

off boost driving and short spool times.... why not NA pistons? working great so far over here on the nor'east coast

I really should hook up my butterflies some day though, even the NA power still feels gutless under 4k revs. I think they are in a mixed up pile out in my shed or garage, wouldn;t even know which solenoids to hook to which connectors, ha.

[float_6969]

My last setup was 10:1 pistons, working butterflies, and a mid-mount intercooler. Very responsive, and still had decent power off boost. Required E85 for any real amount of boost though. Even on 91 octane, I had to pull a lot of timing to keep the knock under control.

[mdb4879]

Ryan, IIRC your current setup has 9.0:1 compression with HKS 264 cams. I know you run E85 and it is beneficial. But just for knowledge purposes to do feel the E85 is necessary with your compression, or do you think the cams extra duration lower the dynamic compression (bleed off cranking pressure) to at or near stock levels and 91 octane (or 93 octane in my area) will provide plenty of knock resistance?

[float_6969]

Current setup is still 10:1 compression and HKS 264's, and the E85 is very nessicary. On my last setup I couldn't run more than 7psi on 91 octane. Anything more and I had to throw so much fuel and pull so much timing to keep the detonation in check that it didn't make much more power. I switched to E85 and haven't looked back.

If I was running 9:1 compression, no, the E85 wouldn't be needed for most turbo's and boost levels.

[mdb4879]

I can't remember where I found all my info on E85, but I saw the math that basically said while E85 has less latent energy than than straight gasoline the extra volume required to reach stoich has more energy as a whole (11% more I think). Do you feel that aside from being able to run more timing advance and leaner AFRs that the fuel conversion alone makes more power? Or is that gain minimal and the power is really in the more aggressive tuning you can utilize? Also, for a given amount of airflow, how much more power do you think one can make with E85 v. 91 octane v. 93 octane?

[float_6969]

The extra power from E85 is twofold. The first is the higher octane (about 105 rm/2), the second is the latent heat of vaporization. These two variables have limits though. The first thing is that if your engine isn't in a state that you have to retard timing, or are adding extra fuel, to prevent detonation, the likelihood of gaining power from E85 is slim.

The conversion alone doesn't make more power. The power comes from allowing for optimized tuning. If the engine parameters are such that optimal timing and fuel values are already being used with the current fuel, then there will be nothing to gain from E85.

As for a given airflow, you can't really compare. There are too many variables to take into account.

[mdb4879]

So aside from high compression and hot air how do you know when the fuel is restricting you and you need to upgrade. I see it's possible to make over 500whp on pump gas, but some can't break 300whp (my speculation, anyways. Those are random numbers btw). I don't know much about tuning, but from what I've read you make more power by more airflow. Changing AFRs and timing to make power is a poor way to tune. You tune these for reliability and make more power through more air. The fuel you use determines the safety margin and with good enough fuel MBT will be achieved well before the knock point (this is when street tuning timing by advancing until you hear knock then backing off a couple degrees isn't beneficial because you could actually make more power with less timing).

I can only imagine with a small turbo being strained the air could be hot and will limit power compared to a properly sized turbo. Even if they are (on paper) flowing the same amount of air you'll have to tune more conservatively with the smaller turbo and won't make as much power. I guess what I'm getting at is if I'm pushing the efficiency limits of a turbo would there be more power to be had with a better fuel? (I know it'd be better to get a better suited turbo than risk destroying the first turbo from straining it. I'm just wondering)

[float_6969]

So aside from high compression and hot air how do you know when the fuel is restricting you and you need to upgrade.

You know because when you are tuning an engine you will hit a point that you're not able to use the optimal timing advance due to detonation. (optimal being the amount of timing that yeilds the most power).

I see it's possible to make over 500whp on pump gas, but some can't break 300whp (my speculation, anyways. Those are random numbers btw). I don't know much about tuning, but from what I've read you make more power by more airflow. Changing AFRs and timing to make power is a poor way to tune. You tune these for reliability and make more power through more air. The fuel you use determines the safety margin and with good enough fuel MBT will be achieved well before the knock point (this is when street tuning timing by advancing until you hear knock then backing off a couple degrees isn't beneficial because you could actually make more power with less timing).

Some of this is true and some is not. It is possible to make 500whp on pump gas. Use a 7L V8; or a 2L turbo with really low compression, LOTS of boost, and a HUGE intercooler, and maybe some water injection. Either one works. The difference is drive ability and power band. The 7L V8 will make more power over a broader range. The turbo motor will make very little power until the turbo spools, then make a bunch of power, and then usually hit redline shortly after. There is a correlation between air flow and power, but the amount of power you make for a given air flow is dictated by the engine's design inefficiency, and tuning for the optimal AFR and ignition timing. Using our 7L V8 as an example, if all other variables are kept equal, there is a relatively narrow range of AFR's that the engine will make peak power at. Too rich or too lean, and you loose power. The same goes for timing. What is often done though is that extra fuel is added and timing removed from the optimal points to compensate for the variations in octane ratings coming from the pump because the engine is often tuned to run near the knock limit of the fuel. If you're running a fuel, such as E85, that has a knock limit far above what your engine needs, then you can run optimal fuel and ignition timing with no concern about detonation.

I can only imagine with a small turbo being strained the air could be hot and will limit power compared to a properly sized turbo. Even if they are (on paper) flowing the same amount of air you'll have to tune more conservatively with the smaller turbo and won't make as much power. I guess what I'm getting at is if I'm pushing the efficiency limits of a turbo would there be more power to be had with a better fuel? (I know it'd be better to get a better suited turbo than risk destroying the first turbo from straining it. I'm just wondering)

Yes, if you're near the limit of the flow capacity of a turbo, running a higher octane fuel MAY be of benefit. That will depend largely on the intercooler. Heat is our enemy here. The reason running a turbo near it's max capacity can be bad for power is because of the amount of heat added to that air. A larger turbo will move the same air with less heat. The issue with a larger turbo is a lack of response. Everything is a trade off.

[mdb4879]

Is there much of a way to tell what fuel you need when building an engine before tuning it? Or do you pretty much have to look at similar builds, wait until you get to tuning, or just plan for better fuel to begin with?

Everyone's going to think I'm crazy for this, but I'd like to see 400whp with a GT2871R. It'd be close, but I think it's doable. I wouldn't have much wiggle room for improvement, but at that power level I don't think I really need much more. I haven't looked too much into it, but I've seen a couple SR's making that power with the 0.64 A/R turbine. One guy I know for sure extrude honed his manifold and turbine housing. So if an SR can do it I don't see why a CA couldn't. That should give the fastest spool possible while still meeting my goal. I'd think with a compression bump and E85 that goal should be made easier. I don't mind running E85 because there are several stations within a few miles of me and more to come. Plus, I don't think it'd harm the turbo any. I wouldn't even hit full boost until 4th, or maybe even 5th gear, and even then I wouldn't even be nearing the choke line until near redline. I don't like going fast, just getting up to speed fast.

[r34 gtr]

Should be doable. We have a member on here making 400whp and 380-ish lb/ft with e85 and a td06 20g. The 2871 compressor flows close to the same (though admittedly not quite as much for the same pressure ratio) so provided you had the proper hot side on it you could probably get close. You might only make it to 350-370, but you would stand a good chance at being close.

For reals though if you want 400whp just get a 2876, gt30r, hx35, 20g, etc. etc. Plenty of better turbos out there for the task at hand. At 400whp the air coming out of the compressor on your 2871 will be roughly as hot as the sun.

[tommey]

Just FYI, a 2871 makes easy 450whp on an E85 CA.

[blownhemi]

The extra power from E85 is twofold. The first is the higher octane (about 105 rm/2), the second is the latent heat of vaporization. These two variables have limits though. The first thing is that if your engine isn't in a state that you have to retard timing, or are adding extra fuel, to prevent detonation, the likelihood of gaining power from E85 is slim.

The conversion alone doesn't make more power. The power comes from allowing for optimized tuning. If the engine parameters are such that optimal timing and fuel values are already being used with the current fuel, then there will be nothing to gain from E85.

As for a given airflow, you can't really compare. There are too many variables to take into account.

Or, actually, threefold. (Let's talk lambda instead of AFR, since we're comparing fuels with different stoichometric AFRs).
- for a given ingoing airflow, it takes more E85 to reach the same LAMBDA as gasoline. So with E85, you're injecting more fuel (by mass or volume)
- E85 has a lower heating value, than gasoline (remember, you're also injecting more of it, because you have to keep the same LAMBDA).

The thing is, these two don't cancel each other out. The ratio of fuelling increase of E85 vs gasoline is higher than the ratio of increase in the heating value of gasoline vs E85, and thus, you end up with more power. You have 20% less power output per liter of fuel, but you are injecting 30% more of it (just some example numbers). There is a cost to this, of course, which is the increased fuel consumption for a given power output (BSFC).

To sum it up, for a given airflow, E85 will yield more power, when fuelling is corrected (increased). This aspect is true on an N/A engine as well. A supercharged engine will have the additional benefits that float_6969 has outlined above.
(Didn't want to mix timing into the above, but you need to correct (advance) timing as well, for the simple reason, that E85 burns slower. But this is true for most high octane fuels, which have no additives to promote faster burning.)

Just FYI, a 2871 makes easy 450whp on an E85 CA.

Hence why you can extract 450whp with E85 from a turbo that maxes out around 400whp with gasoline.