Right guys, my 2l 8v conversion has just received its latest mod- an overbored TB! my neighbour works at an engineering plant near me, and offered to take my TB away and modify it. So, after taking it off and letting him loose on it, it came back with the step removed and polished, screws ground down (spindles left standard) the middle divider fully knife-edged, and the large butterfly was removed, hole overbored by roughly 2mm, and a new butterfly in it's place! we decided to enlarge the larger throttle rather than the smaller one, as the smaller one is there for the throttle response and we didn't want to lose that. Anyway, just fitted it, and ragged it up the road, and it DOES go better! Big difference down low, more responsive, pulls harder. Up high in the rev range it's more difficult to tell, i think it is a bit better. Idles perfectly, too. It will eventually be paired with a flowed and match ported Inlet manifold. My question though, was after modding this, do you think the extra airflow requires more fuelling? I was toying with the idea of winding the AFM spring dial back one step, and trying, but i thought i'd just see what you guys thought first. Also, another point, the full throttle position switch on the top, where abouts (roughly) should that be positioned? it was positioned that it didn't come on until 100% throttle, but i checked another one i had, and that was set to click on at about 85% of full throttle, so i reset this one to about the same.
No, the extra air will be metered by the AFM. Above about 4000 rpm the AFM is fully open anyway, so only a remap would help there anway, or a air temp resistor mod.
sorry, i'm not sticking a 'SUPER CHIP (RESISTOR) MOD PLUSE 200+ bhp ++++' in my car!!!!!! just thinking whether this mod would require more fuel, and what would be the best way to go about that. I have (hardly any) money, by the way, so megasquirt is out of the question!
oh also, if anyone else is interested in one of these, he's going to do another. Like i said, i've noticed a difference, purely by changing this and nothing else
Like mark25 says, any "extra" air now going into the engine is measured by the AFM (as it was before) and the amount of fuel put into the engine is worked out from that reading. In other words there's nothing else you need to do. I'd be interested to see pictures if you have any??
what about once the fuelling is regulated by the ECU(i.e above 4k?) surely the ecu won't know there is more air coming in, as the AFM flap would be fully open anyway? whats the solution there? re-map or nothing?? Also, can anyone give me an answer on the throttle switch at the top, and where that should be positioned? Not sure yet on the prices, but if there was enough interest then it would be an exchange service so we could cater for as many people who want one. turnaround- wise my TB took him about a week.
AFRS after peak torque (AFM slider in optimum position but not full scale defelction) are further enahanced by the WOT switch for rpms byond about 4K. Unfortunalty I have tested the dgifant 2 ecu on my own project before ripping it out and its not very good at AFRs after 4k revs and full load. The mixture goes lean.
2.0 block = BIG LEAN offset in your fuel/engine system. ported TB = LEAN offset in your fuel/engine system. Resistor mod = BIG RICH offset in your fuel/engine system. Bit strange that you are against the only one that is healthy for your car and have done the two unhealthy mods, with no compensation what so ever........ carry on....
hmmm, ive got a 2.0 2e block with 8v head only with exhaust and intake upgraded. and was wondering about this 4k + fuelling issue. what effect would moving the AFM 'wheel' afew teeth have. would that richer the mixure but only under 4k then? by telling the car more air is going in than actually is?. i have one of those 20 ebay superchips sitting about, but the car seems to go well without it so haven't bothered putting it in. should i? is it likely to have a richer top end map? would a rising rate FPR help at all? i notice the car goes v well 3250-5600rpm but dies off after that. i suppose that is normal top end for a digi? i know the 2e blocks are capable of 7500rpm so whats stopping mine from 6.2K+? the 8v's? ,mapping or cam?
Remember Toyotec doing some testing with one of those ebay chips and found that it made the mixture even leaner than the stock chip, and advised against it. . . im sure he will be along to explain more tho
All of the above. Including a 1984cc that has at least 10:4 compression has different airflow and ignition timing requirements. Taken from the old 3A on M/S thread this is what I found between a digifant 2 ECU and a "chipped" ecu. The AFRs are listed on the bottom of the graph. Engine is a 3A Audi 80 unit, Head and block, with ADY inlet and side feed injectors, ABF 65mm TB unported. Cam same as PB one. Fuel was Tesco 99. Two Bosch digifant 2 PCMs used in first comparison AFM teaked to deliver max AFRs later. The Chipped ECU ran leaner that std at lower rpms and loads and produced less torque. Both ECUs ran weak mixtures in the last 1000rpms. Both showed smiliar torque around this point. The car felt alive on the STD PCM and held back with the chipped unit. There was audible knocking at 3500rpm and at 5000rpm on the STD unit made worse when the chipped unit was installed. With the MS PCM, AFRs and spark (not shown) have been tailoured to suit the engine running on Tesco 95. But even with M/S the car still drops off torque post 5500rpm (up 500 rpm on previous tests). However with this set-up torque has increased substanially from low a 2100 rpm. This suggests to me that the camshafts as well as my choice of TB maybe better suited to low down response. Other VW 8v cams are to be investigated.
i'm sorry are you actually recommending i buy one of these and stick it in my car? http://cgi.ebay.co.uk/25-BHP-MOD-CH...ryZ32094QQssPageNameZWDVWQQrdZ1QQcmdZViewItem are you mental? how on earth do you consider this 'healthy' for my car next to tried-and-tested 2.0 bottom end swap???
right then Toyotec, would a custom fuelling remap, by a company such as stealth, be an option here to stop the car running lean +4k RPM? And should i adjust the WOT switch on the TB to come on as early as possible? Like i mentioned, it was set to come on as late as possible, so i just matched it to another TB i had lying around, which was at about 85% of full throttle
Quite interested in your results Toyotec, What was your cam choice for the above tests? Which 'chip' did you actually use for the tests? I know there are quite a few different ones on the market although I suspect they are all from the same eprom map and just carry a different sticker/label. Have you tested any other 'chips' or just the one. Not trying to poke holes in your investigation (you clearly understand this more than I probably ever will) but it just seems like you have quite a few variables in there. The reason I ask is I have RR printouts (allbeit without AFR data) that shows a very healthy torque curve and figures for my 'chipped' 8v.
do you have the before and after data to show it improved power? How was the butt-on-seat testing? An eprom chip is something i would consider, but after toyotec's experiment i was put off. A full remap could be on the cards, but a 30 blitzchip, plus a before and after at RK's rolling road (it would be going there anyway) might be a cheaper option.
