zep Posted May 3, 2011 Share Posted May 3, 2011 Let me preface this by saying that I know very little about EFI tuning, and have only seen the software running once (last night). Hey guys, I've just put a new turbo setup on my car. Old setup: RB25DET T3, internally wastegated, 12.5psi New setup: Master Power GT28, 38mm external wastegate, 14.7psi (if not more). The problem is with my ECU, it's a LINK LEM G3. It appears to have both an RPM cut (soft and hard) and a MAP cut (soft and hard). With this new turbo, the car has become somewhat undrivable if you are flooring it. For example, in 5th on the motorway, if I put my foot down, they turbo will spool but what I assume is the MAP cut will kick in before I even get to 110kph. If I slowly put my foot down I can get up a lot faster. The cut is fucking violent, it's like I'm hitting a brick wall. Is it possible that the tuner set the MAP cut to just above my old wastegate level? And now that I'm going above it it's not having the best of times? The RPM cut is similar. The car feels like it wants to rev above my current hard cut but it cant. This is more obvious if I rev up slowly then hit the cut. It cuts at around 6000rpm. NOW: I had a look at the maps. It appears that the car has been tuned to 8000rpm. Will I have issues if I change my rev cut up to 8000rpm? What about the MAP cut? Any ideas what I can do here? I am toying with the idea of chucking a 10psi spring in the wastegate just to keep it happy... Obviously I'll get it professionally retuned at some stage, but... Not being able to put my foot to the floor sucks! Quote Link to comment Share on other sites More sharing options...
lou Posted May 3, 2011 Share Posted May 3, 2011 In all honesty I wouldn't be putting my foot to the floor without a pro looking at it. Its not just the cuts you need to worry about but also the fuel curve. Putting on a difference sized turbo will fuck with that something chronic especialy when you add in some extra boost. Quote Link to comment Share on other sites More sharing options...
zep Posted May 3, 2011 Author Share Posted May 3, 2011 Would you recommend that I pull my boost pressure down to what it was originally tuned for (or below)? P.S. I always though that ECUs were meant to be smart and add more fuel if you change boost pressure, etc. People are adding boost controllers/other turbos to standard cars all the time. Quote Link to comment Share on other sites More sharing options...
mikuni Posted May 3, 2011 Share Posted May 3, 2011 ^ standard ecu's do try and compensate but with a link you really need to tell it what to do. You can't just tune it to those set perameters and expect it to be completely versatile as you go changing things. I don't know how to help, but I'm pretty sure you shouldn't raise the rev cut to 8000rpm on that thing, it will surely grenade itself up there. Do you have a boost gauge? If so, that you provide more insight into exactly what is going on. You may be overboosting and the cuts are doing exactly what they should do to protect the engine, removing them will not be good. Well, it will be good, very good, but only for a short amount of time. Quote Link to comment Share on other sites More sharing options...
slacker.cam Posted May 3, 2011 Share Posted May 3, 2011 First thing (I forgot to say this before you left last night) is you downloaded the maps/setup out of the ecu right? I suggest the first thing you do is save them somewhere safe just incase you make a meal of it and you want to go back to how it was. You're probably already on to this but just want to make sure... Secondly even if the car hasn't been tuned above your current rev limit the ECU will extrapolate out the top cells so it's not like your car will suddenly stop working. Infact the maps are probably pretty flat up there anyway so it should be fine. If you have a look at a 3D map of fuel and it looks relatively flat above 6k then I would suggest that you're not going to have any big issues in the short term by raising the rev limit. Bare in mind that this is all just my opnion but if it were my car I would happily up the rev limit to 7k just to make the thing driveable. It definitely sounds like it's the MAP cut that's giving you grief though - that's why it sounds like it's not opening the wastegate. What is it currently set to? You 100% need to raise that value up above the maximum boost that you get with your new setup. The easy way to solve the issue is just make it really high (assuming you're confident that your motor can handle the max boost you'll now make). The only other option is to get a lower pressure spring like you suggest. Also, it's always best to change one thing at a time and see how it affects the car. I'd start with the MAP cut as the rev limit shouldn't be mega violent like you're describing. Are you able to take some screen shots of the maps (fuel and ign) and of the map and rev cut screens and post them up? Quote Link to comment Share on other sites More sharing options...
lou Posted May 3, 2011 Share Posted May 3, 2011 Probably wouldnt hurt to. I did a similar conversion on a previous car and fecked around getting it tuned. It was running too rich and gunked up the bearings. Even though I had only put around 1500-2000km's on the clock after an oil chang before making it to the tuner still had to do 3 drops of the oil before he was happy to put it on the dyno. While tuning the bearing let go. Not trying to scare you or anything as I'm sure thats more of a bad luck/worst case scenario but I certainly wouldnt go doing that again. Quote Link to comment Share on other sites More sharing options...
slacker.cam Posted May 3, 2011 Share Posted May 3, 2011 Ring Torque Performance. Ask for their advice on wether putting a different turbo on will siginificantly affect your ARFs. My gut feeling is that it will not. Mostly due to it being only slightly bigger. Id you had changed cams then it'd be a different story. Failing that you're welcome to borrow my wideband tonight and see what the AFRs are doing with the new setup. Brad - why do you say the engine will grenade itself at 8k? Because it's not strong enough, or because you feel that the tune won't be suitable up there? Quote Link to comment Share on other sites More sharing options...
zep Posted May 3, 2011 Author Share Posted May 3, 2011 Thanks so far! Brad: I completely understand what you're saying there. I am pretty sure that I'm overboosting as the car is tuned for a turbo which makes 12.5 psi, and it's now running 14.7psi (the boost gauge in fact seems to go over 15psi). I definitely DO NOT want to grenade the engine. We did have a fiddle with the MAP and RPM cuts last night and it did become much more drivable when we made them higher. However, I am fully aware that this not the best option in any circumstances. A retune is on the cards, but I do need to make it to the Nats! Cam: You sound so optimistic! I am happy that the engine can handle the boost levels, that's no problem, it's whether or not the ECU is giving it enough fuel at this higher level. We looked at the MAP cut and it seemed to be set very high, like 200 kpa but I feel we were reading it wrong (although maybe I saw it hit 250kpa at one stage, but that's like 36psi and I doubt the turbo can even push that/the boost guage says about 15 and there is a wastegate there that I have heard working). I think that the smaller wastegate spring is probably the safest way to go at the moment - what say you people? Quote Link to comment Share on other sites More sharing options...
mikuni Posted May 3, 2011 Share Posted May 3, 2011 [Written before reading zeps last post] Just that it is an older motor with a stroked bottom end. I know the rods, pistons and rod bolts are after market, but surely piston speed at 8krpm would be excessively high. Thats really screaming for an old girl like that, especially boosted and I don't think its necersary. If anything, I would find what the boost pressure is doing and possibly bump up the rev cut to 7krpm. I'd be more inclined to reduce psi with a waste gate spring or boost valve before raising the MAP cut too. Quote Link to comment Share on other sites More sharing options...
slacker.cam Posted May 3, 2011 Share Posted May 3, 2011 I think that the smaller wastegate spring is probably the safest way to go at the moment - what say you people? Totally agree. If you're not confident then drop the boost and make it safer. I am optimistic. If the maps are flat then you can't hurt anything. Having said that - I dont want to be responsible for you blowing motor due to it leaning out... Quote Link to comment Share on other sites More sharing options...
mikuni Posted May 3, 2011 Share Posted May 3, 2011 We looked at the MAP cut and it seemed to be set very high, like 200 kpa but I feel we were reading it wrong (although maybe I saw it hit 250kpa at one stage, but that's like 36psi and I doubt the turbo can even push that/the boost guage says about 15 and there is a wastegate there that I have heard working).I think that the smaller wastegate spring is probably the safest way to go at the moment - what say you people? Atmospheric pressure is 14.7psi or what ever it is, and I'm sure this is added on for the MAP sensor, so that could be right (tuned to about 21psi?). Either way, until you get a tune, why not take the safe route and try to just get the boost at least to a point where you can read it on the gauge. It sounds like some funny stuff could be happening and you're overboosting anyway, so making the engine NOT CUT while this overboost is occuring is not really a good thing. Quote Link to comment Share on other sites More sharing options...
zep Posted May 3, 2011 Author Share Posted May 3, 2011 Oh I can read it on the gauge. BUT, thinking about it now, you are right about the MAP cuts, Boe-rad. The MAP cut is set at 200kpa which is 2 bar (29psi). Atmospheric pressure is 14.7psi and the turbo is boosting 14.7psi = 29.4psi = above the MAP cut. Now wonder it doesn't like me putting my foot down. I have bought a new spring for the wastegate 9-10psi, should keep it happy(er). Quote Link to comment Share on other sites More sharing options...
fishtailfred Posted May 3, 2011 Share Posted May 3, 2011 OK, I got pointed to this thread to comment, so here goes: Just reading the first post, comments are as follows: Yes, your tuner probably set your boost cut just above your previous gate pressure. You can/should move that to just above your new gate pressure, IF your new gate pressure is what you actually want to run, and the engine guts can take what you're trying to throw at them (just see this link for what happens when you ignore engine strength and just make power...). Once you move it there, your higher boost ranges will probably NOT be tuned. They MAY be close enough, but could be far away from correct. In fact, your ENTIRE map could be pretty far from correct due to the increase in efficiency from the newer turbo with better flowing housings, IE, it could be LEAN everywhere. End result, you need to re-tune the car, this is how all MAP based systems are, and why AFM is more convenient once setup. Time for an interlude: PROFESSIONAL TUNING IS NOT NECESSARY!!! nor is dyno tuning, in fact, your average street tune will always be better than your average dyno tune because of the amount of time spent on it, and the variety of conditions under which it operates while being driven compared to faking it on a load cell for a few hours... Interlude two: HAVING A GOOD WIDEBAND ON A TURBO CAR IS NECESSARY, at least while tuning, and desirable all the time to ensure nothing is out of spec and going to cause a melt down. If you have a good wideband on the car, and you have the tuning software, take a log and see what you need to do to the mixtures in various places, see what the timing is like, see where it cuts, and what hte interface tells you about where it should cut, etc. IE, take a friend and laptop out, somewhere quiet and do small test runs and review data and make changes, saving and commenting each file set (tune and logs) as you go. It's fine to make live changes while driving (normal and good) but be aware that if you do, your logs are effectively useless because you wont see where stuff was changed and therefore what hte data means will be unknown afterward. As for the RPM cut, how is the head and bottom end built? At what RPM will the rod bolts say goodbye and leave you with oil on the street and dents in your engine bay? How about the valve spring, cam, rocker situation? float is bad and can cause a dropped valve. If it's built for 8k, sure, raise the limit, but FFS, don't drive it hard there without first easing into those areas and logging and ensuring the AFRs are good and the timing is good and there is no rattling and so on. As for looking at the maps and saying "appears to be tuned to 8k" i assume that you see a table that extends to 8k with some values in it. Do NOT assume that it's tuned to 8k, it almost certainly isn't. If it was, your limits would almost certainly be higher already... Moving to a 10psi spring does not remove the requirement to re-tune for a new turbo/cooler/exhaust/intake manifold/cams/whatever. If you mod the car, expect to adjust your tune, or risk damage. Again, fuck the "pro" tuning, spend the money on putting a wide band in the thing, and learn to tune it yourself (it's really not difficult at all) then you'll understand your machine and its limitations and be in a much more powerful and less vulnerable position. Take my advice on this, even if you ignore all of the other shit above. It is, after all, your risk if you decide to not adjust for new hw and risk blowing stuff up. I understand taking such risks, see above link Other posts: Iou: +1 on on not flooring it till tuned, fuck the pro, though. +1 on the fuel curve being wrong for above explained efficiency reasons +1 on different sized turbo screwing with curves +1 on more boost doing the same, but only for the previous reason, ie, more efficiency. zep: pulling boost pressure down does not solve the problem. your total system volumetric efficiency has changed. what that means is that at the same boost level, you get MORE air (or less, but not the same) and thus the numbers used to calc fuel delivery are now wrong, and need adjusting. ps: MAP based ecus DO add more fuel with more map with all else equal, cept megasquirt2e, but ms is gay, and ken, one of the authors of ms2e, is a moron. If you're reading that ken, feel free to give me your number, we can talk about it pps: standard cars are usually AFM which KNOWS how much air is going in, and to the best of its ability gets it right all the time (the ability is usually too low, though... hence standalones and chips and so on) Mikuni: good point re linearity of boost. a log will reveal this too. you could be spiking above nominal as it spools and tripping a too-close cut. slacker: BIG +1 for saving what is on it exactly as is, and backing that up to email/multiple computers/houses. Adding to that, save and label everything on each session or sub-session such that you have comments on what was better, worse, different wrong, why you changed shit, what you changed weather, etc. Secondly: It's true that it will keep working out the top of the table (probably, unless link really really sucks, which i doubt) but i wouldn't trust it to be tuned to the point of reliability up there, so I wouldnt take the car up there without checking lots of stuff, or making your octane really high (just add 1/3 - 1/2 toluene with your fuel and you'll be good for lean/too much advance while you tune...) Re sounds like not opening gate up: Does the car have a gay screamer pipe? If so, sure, cam is right, it wont open (much) till it reaches target. Is the spring a known value? if it is, what is it, if not, is it chinese? if so, mine was 18psi OOTB (out of hte box) which suited me, but might be too much depending on your engine bottom end, see above link again for a reminder +1 on one thing at a time unless you are certain that you know what you're doing. Interlude, if it has a master fuel value, you could bump it up to be safer for the time being, but you're still risking top end shit being lean because map values can change steeply there sometimes... +1 on screenies of the app and tune. slacker again: define slightly? at low power levels sure, but as you reach the place that was the limit on the old turbo, the new one could be right in the centre of hte island maxing its flow per pressure and minimising its back pressure... ie, we're all guessing, guess conservatively if you like your engine in one piece. Borrow wideband: no wideband???? and you're running into boost cut???? STOP DRIVING IT NOW. zep, 200kpa boost cut is exactly 15psi, that kpa value is from a perfect vacuum, 100kpa is NA. Where is your sensor limit? do not let it go past that, or the ecu wont add more fuel and you'll definitely fuck up... OK, let me reload and make sure no more posts rolled in. OK, good enough, enjoy! Fred. PS, if some CUNT fucks with this post, I will punch them in the face when I get back to NZ. Because 3 years will have passed they wont be expecting it. Saving thread for reference. It's sad when I don't feel like my shit will stay in the thread i post it in... poor form past mods. Quote Link to comment Share on other sites More sharing options...
Spencer Posted May 3, 2011 Share Posted May 3, 2011 ^ no one will delete your post fred Anyway all spot on, get a wideband and put a good road tune on it Quote Link to comment Share on other sites More sharing options...
lou Posted May 3, 2011 Share Posted May 3, 2011 Shit dude, your avatar....your the fulla with the crazy bseries? Quote Link to comment Share on other sites More sharing options...
zep Posted May 3, 2011 Author Share Posted May 3, 2011 Thanks Fred. All this is pointing to me not being able to drive this fucking thing to Nats. I have purchased a smaller spring to get me away from the MAP cut for now as I'm not a fan of it leaning out chronically and having something go disastrously wrong. MY last tune was using an AFR of around 13.0. I believe this is rather high? While I have no way of testing this, the turbo is not hugely bigger than the old one so potentially I will not be increasing my air volume by too much, therefore not leaning it too much. I understand that the compressor maps, etc will cause different amounts of fuel and timing to be needed at different rpm/throttle position. I do not have time to get a wideband and go road tune it. I don't have time to do screen shots and post them up. I am out tonight and tomorrow night am meant to be driving to Palmerston North. Quote Link to comment Share on other sites More sharing options...
Spencer Posted May 3, 2011 Share Posted May 3, 2011 Make some time to get the wideband on the car, then get some GC to tweak things on the way down Quote Link to comment Share on other sites More sharing options...
slacker.cam Posted May 3, 2011 Share Posted May 3, 2011 I love tech threads like this! It's all good information. I mostly agree with Fred (for a change ). The points about tuning it yourself and AFM vs MAP based car are excellent. An AFM car doesnt give a shit about what the VE is as it knows exactly what the airflow is. Whereas with a MAP car the VE is effectively what you are tuning (ie. how much air is actually being sucked into the engine with each stroke). I still stand by my feelings about the VEs not changing largely though. It should have been tuned conservatively last time which will add some safety factor too. I have absolutely no proof of this though. Its just speculation. The VE is largely determined by the flow characteristics of the head and cams. A bigger turbo does not necessarily equate to being a more efficient turbo! The two areas that I am most concerned about are: 1) if the new turbo spools faster then you will need more fuel in these areas, and 2) if the old turbo was running out of puff up top then you will need more fuel up there. Quote Link to comment Share on other sites More sharing options...
KKtrips Posted May 3, 2011 Share Posted May 3, 2011 Nothing like an on the fly roadtrip roadtune - watch Two Lane Blacktop, the passenger changes jets in the carbs like 40 times in a 90 minute movie... Quote Link to comment Share on other sites More sharing options...
zep Posted May 3, 2011 Author Share Posted May 3, 2011 Make some time to get the wideband on the car, then get some GC to tweak things on the way down I wish I had that time, but sadly no. And no GC who has any idea what they are doing, only Thriller, and we all know that he's an idiot Quote Link to comment Share on other sites More sharing options...
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