Brad May

thats one thing i forgot to monitor but im fairly sure it stayed up, i guess if it zeros it possibly is a crank signal. I also checked my fuel cut overrun, its a new tps, but even calibrated reads a low % at cruise so i wondered if it is activating fuel cut

Hi guys, sorry no log yet, but just seeing if this rings a bell with anyone. Atom on LS1 semi sequential and waste spark. At cruise anywhere from 70-100km it will often cut fuel or spark for a second or three then come back on back to normal. The car is an auto, so its not cutting to stall the engine as it comes back in,but allows no throttle input during it and afrs go full lean. Can do it 3 times in 1 minute, then not at all for ten mins, and can be at different revs each time. Fuel press remains constant.

Yes currently true semi sequential . Have not started it like this, but that's how I had it wired previously. Thanks for the advice, I may look at doing that. Yea the iat was never accurate as before all the fuel was on top of the blower

Great thanks for that!

Thanks, yea I just thought adding a couple of injectors also running off the main fuel rail, so essentially running 10 injectors instead of 8, so they will add to the overall map. I also intend to add water/meth as well, but would prefer some fuel going through all the time.

I have a 6/71 blower with 8 port injectors running as semi sequential (only have an atom with 4 drives). I want to add 1 or two injectors above the blower to help cool it. Is my best option just splice into 1 or 2 of the port injectors? Thanks

quick question someone may be able to answer, at idle it sits around -40kpa on the fuel table, someone thought this was really low vacuum? Mechanical gauge shows around 12" vacuum. Bear in mind cam has overlap. cheers

I thought you might. It's only a half hour job to set carbs up on it, so I may just do that tonight to eliminate the ignition side etc since time is not on my side

Funny you ask that, its connected, but just hanging in the engine bay so sees some high temps, however I am sure it is currently disabled towards fuelling etc

Hi guys, can anyone offer any solutions to this? link Atom, LS1, 8 injectors on top of 6/71 blower, waste spark, semi sequential paired injectors. Cam have some overlap (not ideal for blower but sounds great) Have had a couple of tuners look at it, but its doing something really weird. Starts, run, idles. We start to tune the table then (seems to be as it gets hotter) the AFR leans right out (22:1), runs rough and stalls. It will start again, then a few moments later will do the same thing. When it does this it hasn't moved from its box on the fuel table. Fuel pressure remains constant (42psi) throughout. It seems this EFI on the roots blower might take some time to sort properly, so I may chuck a couple of carbs on tonight to get it ready for a holiday and revisit the EFI when I have more time. Any quick ideas?

Well it's going now, what I thought was an over rich mixture was severly lean, and ruined plugs. New plugs and 25% more fuel and it's running great again, well until a proper tune. Can't believe it was so simple

Im still getting trigger errors when cranking so I'm guessing its one of the listed problems like sheilding, grounding etc. As the Atom does not support scope for the triggers I may have to drag it into a shop to get checked out

Update.... New cam sensor in and nope that didn't fix it. Still trys to catch starting and exhaust backfires

Jeez I hope its the same. Cam sensor here tomorrow so will chuck it together and see how it goes. Might just have to chuck a distributor and carbs in it instead!

Yes changed the cam and never rechecked offset etc. Just in buying a new cam sensor now, might as well so I don't have to remove blower and intake again. I just "assumed" the sync would all be identical

unfortunately no, but the trigger error counter started increasing the last time I tried to start it. Half way through blower removal now, so will replace cam sensor and see how it goes.

back again..... so the engine was very sludgy inside (previous owner!) so I thought that possibly the cam sensor was sludged up. Just tried to remove it to clean, and the makers of the blower intake obviously dont take this into consideration. it will only come half out before fouling on the intake manifold. I chucked it back in and just tried to start the car again, after fiddling with the cam sensor now it wont start at all, nearly catches but wont, and nearly blew the exhaust to bits with the backfires it was doing..........so Im guessing I have a crook cam sensor? Anyway, by the time someone replies I will have the blower and intake apart and off so I can get to the cam sensor for replacement.

Just thought of one more thing that I did change, I put a different cam in it, could this affect the cam sensor?

Ok, so as excited as i was still no luck. Here's where I am so far...... Spark plugs are resistor type New Bosch leads spark tested every cylinder - all ok compression tested every cylinder - all ok run it for a couple of minutes, definitely down a cylinder or two, AFR was showing on the leaner side, pulled plugs, 7 & 8 wet, rest lightly fouled. Swapped 7 & 8 coils around with 1 & 2 thinking it was the coils, re run for a minute and pulled plugs. No wet plugs, but all completely dry fouled. This motor run perfect with the turbo setup, then I put the blower on, so the only difference is the injectors are now on top of the blower, left as semi sequential firing. Also relocated the coils from the inner guard back to the original rocker cover position. The fuel map should be pretty close since it was good before. The wideband is in one bank only, and to be honest their is a slightly bad leak in the v-band which is a couple of inches further past the oxy sensor which I know doesnt help. I sent the logs to TECH and they replied today saying the accel enrichment was terribly high and to lower that, but it used to be fine and hasnt been changed? Any more ideas?? @Adamw I have just uploaded log to onedrive, do I need your email or user name to share?

Thanks guys, plugs are ac delco 41-805 which Google's as resistor type. I just got some new decent leads instead of the Chinese ones, so will see how I go today otherwise I will try share the tune another way Adam.

Hi Adam, I have emailed the log to the tech email since I see your on holiday. Here's a question you may be able to answer while relaxing in spa, just a thought, but I just tested resistance on the new leads on it, obviously being ls1 they are short, but they have close to no resistance (not solid core either). Could this be interfering with signals? My old leads had alot more resistance.

Heres a quick log I managed to get, note there is TPS input from me as cold start with no IAC etc. Thanks Bradley LogLS1blower.llg LS1blower.pclr @Adamw

Ok thanks, will be a couple of days before I can. Cheers

Hi there, heres the setup I have... LS1 with cam, 6/71 blower with 8 injectors above firing on semi sequential. Waste spark setup. Had this running fine with a turbo, but now it seems to be misfiring and fouling alot even with a decent AFR. I did the spark test, all are sparking, however this may be where the problem lies.........sometimes when I would go to test the spark in spark test mode by changing from off to on, it would prime the fuel pump all of a sudden. Im guessing I have a wiring problem? or possibly sharing a power feed between fuel and spark that i shouldnt?? Any help would be appreciated. thanks