beninnz Posted February 3 Report Share Posted February 3 I've finally got my new engine in and running in my Lotus thanks to lots of help from the team here. ECU is G4X StormX. Engine is Rover K Series 1.8 4 cylinder with individual throttle bodies. Cams are 288 deg duration, 11.3mm lift with 3.38mm LATDC on the inlet and 3.10mm LATDC on the exhaust (so a fair amount of overlap). I took it to the dyno tuner the other week for the tune, including a full run-in on the dyno as the engine was completely new (self-built). They said they were having issues with erratic vacuum signal / not enough vacuum and couldn't complete the tuning. They thought my cam timing was out (by 30+ deg!) and that this was causing the issues they were seeing. The engine is an interference engine so if the timing was that far out I'm pretty sure I would've had piston to valve contact and it also wouldn't have started/idled as well as it was before I dropped it off to them. I got it home and re-checked the cam timing with DTI gauges - it's bang-on as per Piper's specs for these cams. I've also done a compression test and a cylinder leak down test. Both of those were great, engine seems to be fine from what I can see. I had already connected vacuum lines from the ITBs (behind the throttle plates) that join into a vacuum block. This vacuum block then feeds the fuel pressure regulator and the Link 1.15 bar MAP sensor. The tuner is recommending fabricating a vacuum canister to dampen the vacuum signal from the vacuum block before it goes to the MAP sensor but now I'm wondering if that's even the right path to go down given the cam specs of my engine? They mainly tune Hondas and I'm a bit worried they're heading down the wrong path. Before I take my car back for the final tune, can someone please verify how they think this type of engine should be tuned? I've attached their current work-in-progress map for reference. The throttle response is also really poor, especially from low revs. I can see they've set it up with dual fuel tables. Fuel table 1 uses MGP as load, while table 2 uses TPS as load. The HP Academy courses I've done and webinars I've watched all recommended fine grain steps at low throttle openings when using ITBs but they've got it really coarse (0,10,20,30,40,60,80,100) in table 2 and with no entries for values below 20% TPS. I'm assuming Fuel table 1 is meant to fill in the blanks but given the poor vacuum (to be expected with my cams) I'm not sure that's actually going to work well. Any suggestions here? Thanks in advance! Lotus Elise S2 ITBs - TorquePerformance run in tune map.pclx Quote Link to comment Share on other sites More sharing options...
essb00 Posted February 3 Report Share Posted February 3 Since your engine is on ITBs, it needs to be tuned fully in Alpha-N --- main fuel table & ignition table have to use the Y-axis on TPS (instead of MGP & MAP). How unstable is the MAP reading? Can you also post a PC log (idle and playing with the throttle to show MAP stability)? This is where the fuel equation load source would depend on if Load=BAP or Load=MAP must be used. atlex 1 Quote Link to comment Share on other sites More sharing options...
atlex Posted February 3 Report Share Posted February 3 echoing esb00.. full tps, the map signal with ITBs is almost always too weak for accurate load calculation, especially at closed or part throttle. I've an ITB car with 272 cams and it idles at 70 KPA.. but I know the real idle is more like 35kpa on these engines without ITBs. You don't need dual table fuel yet, so stick with 1. How to setup the break points for the TPS axis? Bare in mind the air flow difference between 0 and 10% TPS is massive, whereas the difference between 70% TPS and 100% TPS barely registers. You want the break points tight gradually increasing as you go up, [0,10,20,30 won't cut it...] start with something more like the fibbionaci sequence and don't be afraid to add more points as needed. Consider something like 0, 0.5, 1, 2, 3, 5, 8, 13, 17, 21, 26, 30, 40, 50, 60, 70, 80, 90, 100 ? Sounds like an awesome engine build. Good luck! Quote Link to comment Share on other sites More sharing options...
KennyJ Posted February 3 Report Share Posted February 3 on itb's you always want to tune in alpha N indeed , why even try with map Quote Link to comment Share on other sites More sharing options...
Adamw Posted February 3 Report Share Posted February 3 Its certainly a pretty odd setup he has done there with equation load source set to BAP, then an alpha N fuel map overlayed with a speed density map... Im not sure if he has out-smarted himself or has ended up with the odd mess when trying to solve a problem. There are some other issues in there such as the IAT trim is still enabled in modelled mode and the charge temp approximation table has zero coolant bias so you will be getting twice as much air temp correction than you should be. Typically for your application just a single fuel table withh TPS as the load axis will do it, equation load source may need to be MAP if any of the bullet points below apply, otherwise load source = BAP will usually work better for NA ITB with high overlap. equation load source = MAP if any of the following are true: The engine has an idle valve The vehicle has vacuum assisted brakes connected to manifold vacuum. The engine is boosted. There is a restrictive airbox/filter arrangement. If you arent in a big hurry, Im in AKL and could take care of it one weekend. Im pretty much booked solid for about the next 6 weeks though. TTP and beninnz 2 Quote Link to comment Share on other sites More sharing options...
beninnz Posted February 3 Author Report Share Posted February 3 6 hours ago, Adamw said: equation load source = MAP if any of the following are true: The engine has an idle valve The vehicle has vacuum assisted brakes connected to manifold vacuum. The engine is boosted. There is a restrictive airbox/filter arrangement. If you arent in a big hurry, Im in AKL and could take care of it one weekend. Im pretty much booked solid for about the next 6 weeks though. None of those apply to me, so sounds like it should be BAP and not MAP as the equation load source... definitely feels like I need to seriously reconsider taking it back for them to finish it given where the map is right now. I'll flick you a PM about tuning it Looks like I can't send you a message (I get an error 'Adamw cannot receive messages') so if you could please message me or let me know how I can get in touch that'd be great. I'm in Auckland too so would be keen to tee something up if possible. Quote Link to comment Share on other sites More sharing options...
Adamw Posted February 4 Report Share Posted February 4 You should be able to PM me now, my inbox was full. beninnz 1 Quote Link to comment Share on other sites More sharing options...
beninnz Posted February 4 Author Report Share Posted February 4 1 hour ago, Adamw said: You should be able to PM me now, my inbox was full. Cool thanks, have messaged you just now. Quote Link to comment Share on other sites More sharing options...
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