ralph

Another option for reference: Lithium battery saves a few pounds at a relatively high position in the car's center of gravity, and provides plenty of Amps. I've heard some caveats about using Li, both because of how they charge and how they spit out voltage, but have had no issues. I did put the Banner back on during troubleshooting an initial engine start issue, but that turned out to be the disconnect switch being miswired at the factory. Because the battery is so much smaller, foam blocks and zip-ties were employed for fitment -- ghetto, but hasn't budged. I have a connector cable for a battery charger on the second (rear) pair of terminals, but rarely use it unless the car will sit for a while (I do use the disconnect switch routinely, just as a habit).

ECU is locked (stock Caterham -- so I don't even think I can view what map is loaded). CC just told me that I should see 4.62v/site=0.0 (descending toward WOT) on Easimap. I'm unconvinced. What makes the most sense with what I've read an observed on the car is that the software is inverting the the voltage (5v system, TPS will read a high value at idle, Easimap will show 5v minus that value); as @sltous showed above, a MM probe on the middle wire of my TPS (with the other to ground) reads 4.60v - the inversion is real. Not to mention, if my TPS voltage was aimed the wrong way, I would not expect the motor to behave well under load at higher rpms, where it is happily hoovering fuel and melting the rear tires. I've gotten some great insights from Andy at PGM, and will likely be rewarding him with the purchase of an unlocked 9M4 with a slightly tweaked version of the RBTB config Caterham uses. Really don't like the element of suspense/mystery in this story, and, besides, what could possibly go wrong if I have more access and control?!! On the tach subplot, I may look at raising to 1PPR, since my tach now reads high, by roughly 2x -- still no rational explanation for why this would be necessary, still draws suspicion to the ECU config.... @KnifeySpoony (et al.) any recommendations for bay area local dyno tuning shops?

AIUI, those numbers should correlate only in that they are two slices of the 5.0v available; they shouldn't be remotely similar. If your Easimap numbers are more in the 0.30-0.50v range, this is starting to look like the smoking gun -- maybe I do have some sort of mapping/config issue with the ECU, but it's probably not the voltage inversion...that appears to be by design and I'll confirm with a MM on the TPS. Will update here when I've had a chance to push the TPS back to site=0.0 at idle and re-do the aperture and flow meter checks.

CC confirms idle should be site=0.0, so I've cranked the TPS too far. They also said the dip switch gymnastics on the tach is normal, but I still don't see why/how. Working theory is that the imbalance of airflow between the barrel sets (1/2 was 2x 3/4) was a bigger factor in causing rough idle than TPS position. I'll focus on dialing that in better and drop my TPS voltage down to whatever gets me just barely at site=0.0. (I think this was around 0.42v as read by Easimap). I have an inquiry into CC to confirm that TPS voltage ascending as reported by Easimap is indeed normal, and the concern about the voltage path being inverted is actually spurious. For anyone on thread who has fiddled with roller barrels, I'd love to hear confirmation as to TPS voltage start point and direction as measured via Easimap vs. multimeter probes on the TPS itself.

From CC, no, just kind of a shrug so far. From SBD, I got a similar kind of non-answer restating that for RBTB the voltage is inverted by S/W; for absence of doubt, when you talk about your setup being at 4.62v, is that the voltage value from Easimap, or from a multimeter on the actual TPS leads themselves?...If the latter, I'm going to have a good laugh and go the probe route in future calibration attempts. SBD also told me to follow the instructions that came with the ECU...what instructions? (not laughing) To your earlier suggestion about just turning the TPS until the engine behaves, I suppose there are two problems with that: as noted before, mapping should correlate with TPS site position (so if I roll that too high at idle, I'm fairly certain this will screw up my mapping...it does backfire a lot like it's on the rich side), but the other that occurred to me after snapping my stock TPS is that if the site position is too high, I may run the risk of exceeding the rotation limit of the TPS barrel with the pedal to the floor, which would not be a good thing -- floored WOT and the TPS barrel snaps?...no thanks. I'm starting to wonder if maybe I've been overcorrecting this the entire time, making the engine run way too rich, and buggering up the mapping with way too high a site position. My assumption was if I want higher rpm at idle, I need higher voltage (as read by Easimap, which shows voltage ascending as throttle opens). I'll keep fiddling with it and report back here once I get it working properly...

tach: all dip switches off except #8, and the tach seems to behave (down to .5ppr vs 2ppr) idle: cold idle is still not a thing at all, but the engine warmed up will idle stably at .50v/2.9site (which seems pretty off, imo)

CC responded and advised that I just drop the first two dip switches on the tach (to reduce PPR) -- seems a bit ham-handed, but I'll give it a go -- also, still no explanation for why this particular variable would change from 9a4 to 9m4 (which are supposed to be able to run with equivalent configs -- begs the question as to exactly what config I was shipped). Hopefully this sorts the tach. As for TPS/mapping, turns out, I'm the first customer to use a 9m4 with RBTB, and since their R&D is essentially customer funded, there we are: tabula rasa. The working theories don't make sense to me (i.e. if the voltage *should* start high and descend as throttle opens, how I'm I able to drive this thing with WOT approaching redline and have the engine basically going gangbusters?). It is certainly starting to look like the 9m4 they shipped has a bogus config, but as to what the right one is...that seems a very open question. Again the symptoms are: very low idle even well past site 0 (2.9) on the TPS, and engine won't stay running when cold, plus a bit of backfiring when backing off the throttle quickly (to me that reads: too rich, but maybe it's normal rbtb behavior?).

I paid use tax in full (~$5200) at the DMV shortly after completing the build (approx. 6-7mo after receiving the crates). If the CDTFA wants to charge me interest on the 6-7mo delay, I have no quarrel with that, and will happily pay it. What they are asking me to do is pay tax I've already paid (plus a year's interest), which is not right, IMO.

If you've dealt (or are dealing) with registering a Caterham in California, read on... (I'm dropping this in build threads since that's where it's likely to reach folks who may have opinions on it and/or might benefit from being aware of it -- not technically a build thing...more a bureaucratic thing.) Just got notice from the State of California (CDTFA) requesting that I pay use tax (with a year's worth of interest). They had reached out a couple months after my crates arrived, and I had explained (I thought successfully) to the agent that the reason I wasn't paying use tax as part of the import process was that I would be paying it upon registering with the DMV. In this second notice, the situation is characterized as my "claim for exemption has been denied"...which I think is a bit off from the actual situation -- I'm not claiming an exemption per se, but rather pointing out that I have in fact payed use tax, and would prefer to not have to pay it twice. I've sent them all relevant paperwork (though the DMV record of 'fees paid' doesn't specifically mention "use tax"), and am waiting on a reply. I'm guessing that with such a low volume of the particular scenario (sb100/SPCNS) involved, the CDTFA folks are confused by it, and just see someone importing car parts (which would be subject to use tax at the time of import). Has anyone gone through this contention as part of registering their Caterham in CA?...any suggestions?

re: tach removal...duh!...yeah, that's super easy -- my dip switches are: 1,2,8 on (which sounds right from what I've read) re: TPS, will try that, but doesn't increasing site position mess with the overall map?...doesn't it expect something close to "0.0" at idle? re: redline, dunno...tach is still on drugs...haven't hit the rev limiter, so there's that; I definitely like the noise this thing makes now, and more so the response/pull (laggy/weak with the plenum) ...if I can't fix the tach thing with dip switches, I'm probably going to have to get the ECU reflashed, which is beyond annoying at this point.

Ah, so in theory, with a mirror, I could set the dipswitches without removing the tach....still not sure how to remove it....not seeing those 'thumb nuts' others are talking about. Notwithstanding the tach being on crack and the idle being low/rough, I've managed a couple spirited blats in the SC mtns, and find that a slight nudge of the throttle at a stop will keep the low idle from being a problem. I drive with a shoeless right foot, so I can finesse it with my small toes without too much trouble. For anyone following the idle metrics, I'm at .45v/site=1.7, and it's still acting like it's at 500rpm. I might try going a bit past 6mm on the idle screw and try to get a voltage at site 0.0 that works. I'm assuming that you want idle at 0.0 for the rest of the map to make sense. All that said, this engine now pulls like a slingshot once revs are north of 1.5k or so, and it has no trouble eating as much gas as you can feed it (plenum setup bogged a bit). Passing folks is a breeze, and I feel a vague whiff of contrition knowing my exhaust pipe is aimed at the driver I'm passing -- sorry, not sorry...

If I read the related threads correctly, I need to flip some dip-switches in my tach to get it to agree with the ECU (1,2,8 should be on...implying there's something with the crank/pulley ratio (i.e. 2 pulses, not 4)). Thing is, everything else I read about the tach suggests I may have a different tach (see pic, no wrench-free nuts to detach evident).

Idle is low-rpm and rough (not quite as rough as when cyl#1 was dead). As far as sync goes, I'll use a flow meter before I start fiddling with bleed screws, and, as you observed, they do seem aligned well within the pairs (I could see the balance screw working loose and making things interesting between the 1,2 pair and the 3,4 pair, but, based on the drill blank used to measure the 6mm, 1=2 and 3=4). Pull's great once I'm up around what I'm guessing is 2krpm, revs great from what I think is 1krpm -- in general it's way more responsive and doesn't bog the way the plenum setup did. Also seems like less finesse/precision is required in what you do with the throttle when letting out the clutch in first (peeve of mine with the stock setup). Glad to hear the tach is an easy fix, just a little annoyed (though not surprised) that this sounds like something that should have been specified in non-existent instructions. I have not heard that the tach would need to be adjusted, and the 9m4 (per SBD) has exactly the same pinout as the 9a4, so I'm not sure what's different...sending different voltage to the tach?...this spooks me a bit.

Still struggling with idle, will crank the TPS past site 0.0 and see if that helps, and will tune the barrels via bleed screws. Also, my tach appears to have lost its marbles: registers ~400rpm at idle (which may not be too far off -- definitely too low still), but sweeping up through the revs, it never really gets much past 1100 or so... no word yet from CC on what the idle voltage should be on the 9m4 with rbtb...wonder if i got the wrong map...

...something more like .42v at .07 seems to work!...I'm guessing there are actual target numbers for the 9M4, but only Mr. MBE knows for sure... Idle's a little rough, but throttle is more responsive off the line, and holy crap those horns howl...my new favorite sound. will do some fine tuning with an anemometer and might play around with the voltage some more. Pretty stoked to have this thing back on the road; just need to salvage my chainsaw surgery on the bonnet somehow...