H22 build-up – part 4: transmission & drivetrain
Reliability & Strength:
For the most part, F & H series transmissions are pretty damn strong. On a naturally aspirated application, you’re not going to be seeing anywhere near enough torque for the raw strength of the transmission to become an issue.
However, like most modern trannies on the road, the synchros will rarely last very long if the box sees any abuse (speed or power shifting, etc.). And there is an issue with the 5th gear/reverse shifter fork – basically a product of a poor design. If it gets bent, you’ll find that 5th gear starts grinding, and putting it in reverse can become difficult or impossible. There is a TSB available from Honda on the subject, but reports from people who have had it done are rarely positive, as the problem returns in a few thousand miles. For the nitty-gritty on whats actually happening, check out the writeup done by Marcucci in the General FAQ section of www.preludeonline.com.
Unfortunately, there’s little to be done to avoid the problem other than being careful with your shifts. And if you’ve got the notorious 5th gear grind, make sure to treat that shift like its glass to prevent a problem with your reverse. But there’s really no need to slam your gears anyway, and even speed-shifting serves little purpose for the vast majority of your time in the car. The cable tranny on the H/F trannies isn’t quite as forgiving of a sloppy shift as the rod-actuated ones on most B series, and there are no affordable aftermarket replacements. So relax a little and take an extra .3 seconds per shift, and your tranny & synchros should reward you with a nice, long life . . . .
Clutch
First off, just because clutch A has a higher torque capacity than clutch B doesn’t mean it’s the better choice. Put too hard of a clutch on your engine, and you’re just gonna end up with a dead leg & a car that’s obnoxious to drive. In fact, due to the Attack’s light weight, the need for an aggressive clutch is reduced even more. A “sport” one rated at a ~33% increase in torque capacity should be enough clutch to handle the hairiest of naturally aspirated motors – and the vast majority of boosted ones as well. In fact, unless your eventual goal is to put down numbers somewhere north of 220 whp, I would say an OEM replacement clutch will be plenty strong for an Attack. Exedy makes a stock replacement kit that costs around $100, most “sport” or "organic" ones (the ACT HD-SS & Exedy Organic to name a few) will cost somewhere in the $220-280 region.
Flywheel
Upgrading the flywheel is an excellent way to make a dramatic improvement in the performance of your engine. The stock flywheel weighs around 18.5 lbs – this is inertia that the engine has to accelerate & decelerate every time you rev up & down. By reducing this inertia, you can gain a noticeable improvement in engine performance, especially in the lower gears. They also make rev-matching a lot slicker (throttle blips will only take a fraction of the time they used to).
Although it’s possible to have a machine shop simply lighten your stock flywheel for a small fee, I wouldn’t recommend this method. Not only are you taking the chance of weakening your flywheel to the point where it could become dangerous, but the majority of material that’s “easy” to take off is located at the center of the wheel, which is less effective at reducing the inertia of the piece.
So you’re looking for a piece made from either aluminum or chromoly, weights typically range from 8-12 lbs. – look to spend around $150 to $250 for one. Just make sure that whatever you get has the appropriate timing marks (TDC & 15 degrees BTDC), and that the teeth are beveled to match your starter properly (there were some a few years back that ended up chewing up people’s starters because they were cut to match the JDM starter, not the one that came in our cars). Fidanza, ACT, Clutchmasters, and XTD are some examples of common brands.
Limited Slip Differential (LSD)
The goal of a limited slip is just what it says – they limit the amount of slip from any one tire. In a standard open differential, power always try to follow the easiest path. So if one of your wheels starts spinning (like the inside tire in a corner), all of your available torque suddenly becomes dedicated to pulverizing that tire instead of propelling you down the road.
To avoid that sort of peg-leg performance you use a LSD – these have the task of locking the differential if one wheel begins spinning faster the other, while at the same time allowing the wheels to turn at variable rates to some degree (like they need to when you’re cornering). There are 3 basic classes of LSD’s: viscous, clutch, & helical (or torsen). A full comparison between these categories is beyond the scope of this article, but a quick search with your favorite search engine should bring up plenty of reading material. For the (non-ATTS) F/H series transmissions, we’ve got 3 basic options available to us – Honda OEM (helical), Kaaz (clutch), and Quaife (helical).
If you can find one, an OEM LSD-equipped tranny is a worthwhile option. They came on the S spec JDM Prelude and on a couple different performance slanted Accords that were available overseas. While it’s not as aggressive or noticeable a LSD as a Kaaz or Quaife, it gets the job done, and is certainly better than nothing. And if you can find one, the price is often pretty reasonable (usually +$300 to the price of the transmission it comes in). Of course, you’ll usually need to buy the entire tranny at the same time, which both simplifies & complicates matters. It’s simpler since you’ll be able to just swap in the entire LSD-equipped transmission for your old one. But, of course, you’re also spending more money for the tranny itself, and you may not always be able to recoup your expenses by selling your original one. But as a side benefit, a LSD equipped Honda tranny often comes with slightly more desirable gear ratios . . . see below for more details.
The other two aftermarket options (Quaife & Kaaz) run about $800-$900 before installation. They are both excellent units, but they aren’t cheap – and installation involves removing & pulling apart the transmission, which is not a simple affair. I would highly recommend finding an installer who has experience in installing LSDs in Honda FWD drivetrains for this type of job.
One product I haven’t mentioned yet is the Phantom Grip - a low-cost “alternative” to a limited slip . . . there’s not a whole lot of people out there that have tried it, but it seems like for every report I’ve read of someone installing one & it working well, I’ve read another one where it fragged up their differential beyond repair. Personally, those aren’t good enough odds for me to feel comfortable using one. So unless you’re using a throw-away tranny & have another one lined up ready to go, I recommend saving up the extra money to get a real limited slip.
Final Drive gear
The stock final drive ratio on the H22 transmission is a 4.266:1 ratio – this is pretty aggressive, but some startling improvements in acceleration can be found by using an even higher one. Labor involves disassembly of the transmission to replace the stock final drive ring & pinion gear with the new piece. If you happen to be installing a limited slip differential, it would obviously be cost-effective to do both of these at the same time . . . .
For options, Prodrive is the only company I’m aware of that makes that make a final drive for the H/F series transmission – it’s a 4.71 ratio, and retails for about $1,250. Other companies such as Houseman Autosport will make a custom one for you for about $1,500.
So this obviously isn’t a modification for the faint of wallet, but an upgrade from 4.266 to 4.71 will grant you a ~10% increase in torque at the wheels in every gear, at every rpm – that’s a massive improvement. Of course, the downside is that rpm levels at every speed will increase by ~10%, and maximum speed in each gear will be reduced by ~10% (unless you raise your redline). For a daily driver, this may not be desirable for some. But for a weekend vehicle like the Attack, I say pile on the gearing . . . .
Alternate Honda gearboxes
At last count, there are close to a dozen different F & H series transmissions that will bolt up to the H22. The majority of them (like the F-series ones) have a taller final drive ratio and won’t be a very desirable match with the H22’s power-band, so I won’t bother addressing them here. But there are a few gearboxes that were available in one model or another that have ratios that are slightly more aggressive than the standard ’97-01 5th generation USDM model (the M2Y4).
***transmission disclaimer***
Trying to find reliable information on the different tranny codes & gear ratios on these boxes is pretty hard. I’ve done the best I can to compile the available options & present accurate information here, but I wouldn’t be surprised if there are mistakes . . . .
M2F4: These came in the USDM 4th generation VTEC Prelude (‘93-96), so they would be the easiest one find in a local junkyard (although the car is still far from common). All it’s gears save for 2nd are slightly more aggressive, while second is a tiny bit longer. Frankly, my only complaint about the 5th gens gearing is that 2nd is too tall already, so this box will only exaggerate that with its shorter 1st gear
M2B4: This box came on JDM VTEC Preludes and has identical gearing as the M2F4 listed above, but it came with a LSD (note that the M2A4 variant did not).
U2Q7: Found in the European Accord Type R, this has a first gear that matches the ’97-01 box, but it’s 2nd through 5th are the tightest you can find on a stock tranny. It also came with a LSD. For a non-daily driven car (or one that sees little highway time), this would be my choice of trannies. They’re hard to find though.
T2W4: This came from the Accord Euro-R (a JDM model), and has gearing identical to the
U2Q7 above, save for a more relaxed 5th gear that is the same as the ’97-01 model. The combination of good 1st gear placement, an aggressive 2nd through 4th, and a semi-relaxed 5th make it very desirable to enthusiasts – especially since it also came stock with a LSD. But they’re quite rare, so best of luck sourcing one.
T2T4: This came in the Accord SiR-T (the F20b engine). This box is kinda cool since its 1st through 4th gear ratios are identical to that of the 5th gen Prelude we got stateside. The only difference is that it has a taller 5th gear which is nice for highway driving, and it has a LSD.
For my own purposes, I maintain a little excel worksheet in order to keep track of all the tranny codes and their respective gear ratios. So if anyone’s interested in more specifics than I have here, let me know & I’ll e-mail you the section that pertains to the H & F series transmissions.
H22 build-up – part 5: fuel/ignition tuning and knock detection
So once you’re ready to move beyond the basic bolt-on modifications, many people will tell you the next step is to upgrade the cams/valvetrain and get some headwork done. I disagree with this.
If you’ve chosen your parts with care & they’ve improved airflow as intended, your engine should be pumping enough air over stock trim that your stock fuel & ignition maps will be pushed to their limits. The stock ECU is capable of adjusting fuel trim up to 30% richer or leaner than stock, which for a speed-density system is fairly flexible (there’s no MAF to physically measure the amount of air the engine’s pulling in). But once you reach the ECU’s limit to compensate for added airflow, it’s very unlikely you’re going to see much more power, no matter how many parts you throw at the engine. And there’s a good chance you’ll be compromising reliability as fuel maps & ignition timing become less & less appropriate. So before you go any farther, right now is the time to step up & tune the computer.
First, a few notes about Honda computers. Until the advent of the new K-series 4-cylinder engines Honda’s been using the past few years, the computers are not flash programmable. What this means is that the stock computer is notoriously difficult to “chip”. There are replacement “chips” available out there, but I would steer far, far away from them – they’re most often just a copy of the Mugen program that tweaks ignition timing, leans out the air/fuel mixture, and gets rid of the rev limiter and trouble codes. The chances that one of these generic chips will be a good match for your engine are very slim.
Options
So with the goal of being able to tune specifically for your setup, there are three basic methods available. The first is by using a complete stand-alone system. Examples of these are Microtech, Force EFI, Haltech, Motec, & TEC. These replace your entire computer & wiring harness with their own components. Their flexibility is endless, but they are notoriously difficult to install & tune. Just getting the engine to run at all can take a lot of time, although some have base maps available for different engines & setups which can speed up the process. The listing of stand-alones above is by no means comprehensive, so you’ll have to check around yourself if you’re in the market for this type of system.
The second group of engine management systems are what I call “intercept” systems. The AEM PMS, EFI systems, Zdyne, Greddy e-manage, and Apexi VAFC all fall into this category to varying degrees & extremes (although one could argue that the AEM one belongs in the stand-alone group). Basically these work by intercepting the stock sensors at the ECU, and modifying the signals (or supplying it’s own) to suit it’s own purposes. This is a fairly popular technique, as it often allows the Honda ECU to continue controlling all the countless periphereal functions that can be so tedious to set up & get working properly on a full stand-alone. Once again, there are probably systems available in this group that I neglected to mention.
The third group really only has one player – Hondata. This is the only company that has devoted the R&D to actually hacking the Honda programming, and supplies the hardware & software to dyno tuners & end-users so they can write their own chips. However, Hondata doesn’t support all Honda ECU’s – most notably, they’re unable to work with OBD2 computers. So an OBD1 computer & conversion harness will be necessary if your engine is OBD2. Nor does Hondata support the H series ECU’s – not enough demand to bother figuring out it.
But any OBD1 ECU from a VTEC Civic (P28) or Integra (P72) is capable of running the H22 given the proper fuel & ignition maps. Just make sure to read up on any features you might lose by going to the P28 or P72 (like the knock sensor or IAB’s). Personally, I think the P28 is the best option – it’s way more affordable than the P72, and even though you lose knock sensor & IAB support, IAB’s can be controlled via the nitrous actuation function that comes with the Hondata setup, and there are more accurate ways to control the knock sensor . . . . .
Knock Sensor
Now, the stock H22 comes with a knock sensing system – the sensor is mounted at the back of the block, and below 5,500 rpms it protects the engine from pre-detonation by retarding ignition timing when knock is detected. This works fine for people with stock engines who put in 87 octane swill by accident, but we’ve now begun to modify the powerplant fairly far from it’s original parameters. I’ve read about quite a few cases where the stock knock sensor & ECU weren’t terribly pleased about all the new noises the engine was making, and started pulling ignition timing to try & rectify the situation when nothing was really wrong. This, of course, results in reduced performance, crappy throttle response, and an engine that bogs when you least expect it (all symptoms that are notoriously difficult to troubleshoot). Not to mention, many engine management systems don’t support the use of the factory knock sensor. So now is an excellent time to upgrade to . . . . a J&S Safeguard system.
This unit utilizes your stock sensor to control pre-detonation to an incredibly fine degree. While this may seem like overkill for what is basically just a bolt-on engine at this point, it provides the ability to tune your engine much more aggressively than you would (or should) be willing to try without it. For about $350-500, it’s peace of mind that’s not to be underestimated – especially if you have any intentions of tuning the car yourself.
Tuning
Regardless of what engine management system you choose, it will require tuning for your engine to run properly & make good power. You can either get the name of an approved tuner in your area straight from the manufacturer of your engine management system, or better yet – choose your engine management system based on what your trusted tuner of choice is familiar with using . . . You can have the best engine management system & the most capable tuner in the world, but if he/she’s not familiar with the system, it’s not likely to be a very satisfying experience. Even in a best case scenario, be prepared to drop some semi-serious cash for access to dyno facilities & a technician (at least a half day’s worth of tuning, usually at $100+ per hour).
Although if you like to figure things out for yourself (a good bet if youve gotten this far . . . ), you can do a lot of the tuning yourself with a good wide-band O2 sensor & datalogging capability. A wideband O2 sensor is different from a standard sensor in that it reads 0-5 volts vs. the 0-1 volts a standard one puts out. This means the resolution is accurate over the entire air/fuel spectrum, and not just a narrow range like on stock sensors. Narrow-band sensors are fine for their intended purpose (keeping you as close as possible to 14.7:1 air/fuel during part-throttle conditions), but they’re notoriously inaccurate when your air/fuel ratios stray too far from stoichiometric. And for safety’s sake, at any kind of aggressive throttle position or load you’ll probably be tuning for a good bit richer than that (anything from 12-13.5:1, depending on your application). So in order to measure those richer air/fuel ratios with any kind of accuracy, you need a better sensor.
Wideband systems have recently started to become fairly affordable, due to the availability of a new Bosch sensor that only costs about $30 (comes stock on a couple new VW’s). To get an idea of the systems available to control this sensor, check out this thread over on Honda-tech.com. Full setups can now be put together for only a few hundred dollars, where as just a few years ago you couldn’t find one for under a grand.
With a good wide-band sensor set up & the ability to datalog, it’s possible to do all of your fuel map tuning on the street instead of spending long hours on the dyno (which quickly gets expensive). Street tuning is becoming more and more popular for enthusiasts, since real-life driving scenarios (part-throttle, light-load, tip-in, etc.) can be difficult to recreate in a dyno situation – or impossible on a common inertia setup like a dynojet.
And some systems (the AEM PMS comes to mind) even offer an “autotune” function that writes it’s own fuel-maps as you’re driving by using the wideband O2 sensor readings & a target a/f ratio (basically an advanced closed-loop setup). You still may need to hit the dyno to figure out what to do with your ignition maps, though – although it’s theoretically possible to tune those by yourself as well by using a combination of a G-sensing “dyno” (G-tech or an equivalent) and a J&S Safeguard for your safety net. Just make sure you have an appropriate place to do your tuning . . . . Non-residential, lots of space, and no traffic. It’s a rare neighbor that will appreciate you tuning full-throttle acceleration passes past their house . . . .
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