chilli Posted November 6, 2005 Share Posted November 6, 2005 I've been BPU a few weeks now (but not done many miles so far, most of them not at WOT anyway) but I've been wondering: Now the weather is getting properly cold I notice that I'm boosting at about 1.15bar then rising with revs to just over 1.2bar at high revs (don't think it's reaching 1.25 peak though, not seen that yet). Should I be concerned about this (since it's just over 1.2bar)? Also, I've not had a chance to fit the fuel pump (being a bit pedantic about how I'm fitting it). I guess I need to do this asap, again, should I be overly worried though? If it's seriously risky then I'll drive sensibly until it's installed Also, when I first got it, it seemed really quick to high revs 7k, now (this maybe subjective) it definitely pulls harder, but seems to tail off slightly at higher revs, making it seem better to change gear earlier than before. Is this normal. I'm thinking the extra torque and bhp are peaking lower down in the rev range and since the turbos are flat out at 1.2 bar maybe the efficiency now drops off more at high revs, does that sound about right? Link to comment Share on other sites More sharing options...
Tom Posted November 6, 2005 Share Posted November 6, 2005 I believe that it should hold peak till redline, I would probably worry about that fact your hitting 1.25 with no walbro and I'm assuming 440cc injectors still?, If it was me I'd take it easy till these were fitted, all imo of course:) Oh then get it tuned! Link to comment Share on other sites More sharing options...
Homer Posted November 6, 2005 Share Posted November 6, 2005 Sounds normal. The peak bhp is around 6000rpm, so there's no point reving beyond this. However when I first decatted I felt the power leveled out quite quickly, then I fitted the FMIC and it made a huge difference. The power didn't really level off until over 6000rpm. The old IC wasn't knackered but it had certainly seen better days... whats the one on your car like? Link to comment Share on other sites More sharing options...
chilli Posted November 6, 2005 Author Share Posted November 6, 2005 Thanks It does hold peak till the redline, it's more that the acceleration seems to be tapering off very slightly, and changing to the next gear is better - probably better for the engine too I guess. Just wondered if others had noticed this? Well, my plan is, get the Walbro fitted asap then I'd like an aeromotive fpr and emanage ultimate and a trip to the rolling road Edit: I did take a peek at the SMIC through the front ducting, it looked "reasonable" I thought, couldn't see crumbling bits. Maybe I should take some pics and post up for opinions? Hmmm do I see an "unbudgeted" CW SMIC or FMIC on the horizon lol I wonder if I could fit a temp sensor to see if the SMIC is working well or not? Link to comment Share on other sites More sharing options...
Steve Posted November 6, 2005 Share Posted November 6, 2005 What about bigger injectors? Link to comment Share on other sites More sharing options...
Tom Posted November 6, 2005 Share Posted November 6, 2005 I'm assuming 440cc injectors still? I've never seen a car being tuned on the rolling road, maybe someone will organise a RR shootout again soon. Link to comment Share on other sites More sharing options...
chilli Posted November 6, 2005 Author Share Posted November 6, 2005 From what I understand 440 injectors are just fine to the max the twins are capable of, the FPR can be used to adjust fueling if required because the injectors are maxing out. Link to comment Share on other sites More sharing options...
tbourner Posted November 6, 2005 Share Posted November 6, 2005 Yeah sounds like you need the Walbro in asap. SMIC may well be fine you need an EGT gauge really. I get max power at 5500 and peak torque at 5000, so changing at 6k revs is about right, no need to go to redline. Guessing yours will be a similar thing. Link to comment Share on other sites More sharing options...
JohnA Posted November 6, 2005 Share Posted November 6, 2005 Without checking on a wideband I'd be careful in boosting a JSpec beyond 1.2bar, especially in cold weather. You never know. Plus it's anyone's guess when the turbine wheels will decide to go for a walk. Take it easy. After one bar the returns (in bhp terms) start to diminish very quickly. I've managed to push it a bit further with my 'misty' setups, but it still tails off after 1.1bar. Even with 99RON fuel + quite a bit of methanol. I'd expect it to be much better with race fuel, but that isn't a roadcar any more, is it? Link to comment Share on other sites More sharing options...
Nic Posted November 6, 2005 Share Posted November 6, 2005 From what I understand 440 injectors are just fine to the max the twins are capable of, the FPR can be used to adjust fueling if required because the injectors are maxing out. I wouldn't necessarily agree, I was seeing 90+ duty cycle with stock 440cc injectors, turbos and fuel pressure increased using FPR at 1.2bar, at dyno figure of 429hp, so fitted bigger injectors. Bigger cams will help keep the engine pulling at the top end. Link to comment Share on other sites More sharing options...
dangerous brain Posted November 6, 2005 Share Posted November 6, 2005 Mines on 440cc's and that is doing 395 at the hubs. That was at 1.15 bar. Power drops off after that boost figure so there is no actual advantage on my car to boosting above that figure. Link to comment Share on other sites More sharing options...
adi2009 Posted November 6, 2005 Share Posted November 6, 2005 I wouldn't necessarily agree, I was seeing 90+ duty cycle with stock 440cc injectors, turbos and fuel pressure increased using FPR at 1.2bar, at dyno figure of 429hp, so fitted bigger injectors. Bigger cams will help keep the engine pulling at the top end. Nic, what was the ambient temperature that you saw that bhp figure? Also was it measured at the flywheel? Link to comment Share on other sites More sharing options...
Nic Posted November 7, 2005 Share Posted November 7, 2005 Nic, what was the ambient temperature that you saw that bhp figure? Also was it measured at the flywheel? I think from memroy it was done in November, so probably mid 20's. Yes that was estimated flywheel. Link to comment Share on other sites More sharing options...
chilli Posted November 7, 2005 Author Share Posted November 7, 2005 Thanks guys for the response. From what I am hearing, that there is little benifit in holding it in gear to 7k rpm and since I've also noticed a slight tail off in performance at high revs, I'll try and change up around 6k or so from now on. I don't think changing the cams is a priority for me, probably good for engine life not to 'rev the nuts' off of it anyway. Since the boost seems to rise with revs, I think this will tend to keep the boost at or below 1.2 bar anyway (it was only peaking above 1.2 at very high revs in 4th, above 6k). It's only during this cold weather that the boost has been a tad higher than I might have liked, so I don't think I'll be changing the restrictor ring, it was just below 1.2 at the end of the summer which felt like a safe limit. As for the injectors, well I'll have to see I guess. I plan to stick with 440s and since they have worked for others I'm hoping mine will be the same. If the dyno session shows they are maxed out and my afr's are going too high then I'll of course change them asap. I forgot to mention, I intend to fit a wideband O2 and egt at some stage soon also, so much to do, so little time lol thanks for the advice Link to comment Share on other sites More sharing options...
JohnA Posted November 7, 2005 Share Posted November 7, 2005 yeah, no point in trying to squeeze the last drop of performance at 7Krpm, the stock cams are designed to counteract the extraordinary backpressure created by the stock twins, so they are a bottleneck at that point. Link to comment Share on other sites More sharing options...
dangerous brain Posted November 7, 2005 Share Posted November 7, 2005 I can reccomend the HKS 264 cams. The guys at thor chalked the power my car is pushing out down to these cams. Mine started to run a tad lean at the very top of the rev range on 440's with a walbro pump and FSE but an expert or other said that the supe engine fared better than most engines under lean conditions. Link to comment Share on other sites More sharing options...
chilli Posted November 7, 2005 Author Share Posted November 7, 2005 how lean is lean? I'm not saying I won't change the cams at some stage, seems lower down on the list at the moment though really. Cheers for the info though, it's all useful stuff to know. Link to comment Share on other sites More sharing options...
Ian C Posted November 7, 2005 Share Posted November 7, 2005 I think you are noticing a power drop-off because the turbos are out of puff. To maintain 1.2bar of pressure at 7000rpm they need to flow twice as much air as 1.2bar at 3,500rpm. Just because you can maintain that pressure lower down the rev range doesn't mean the turbos can flow enough to feed the engine at the same pressure higher up. That's why you have two sequential turbos - the first one simply can't flow enough air above about 4000rpm. They can manage say 1bar at max rpm, but at 1.2bar they are overspeeding and overheating the intake charge, hence the noticed drop off of power. -Ian Link to comment Share on other sites More sharing options...
dangerous brain Posted November 7, 2005 Share Posted November 7, 2005 OK AFR goes like this 2000 rpm 15.2 torque 128 ft/lb BHP 49 3000 rpm 14.9 torque 271 ft/lb BHP 158 drops at 3500 rpm to 11.6 by 3700 rpm 4000 rpm 11.6 torque 341 ft/lb BHP 261 jagged line onwards torque peak @ 4571 RPM 376.9 ft/lb 5000 rpm 11.6 torque 370 ft/lb BHP 358 PEAK POWER @ 5892 RPM OF 395.2 6000 rpm 12.0 torque 340 ft/lb BHP 394 6667 rpm 12.39 torque 304 ft/lb BHP 380 Link to comment Share on other sites More sharing options...
Ian C Posted November 7, 2005 Share Posted November 7, 2005 Nowt really to worry about there mate, anything leaner than 12.7 maybe. You intake charge temps may be an issue around there, have you had it checked for det up top? It's probably not happening but you strike me as somone who wants to make sure -Ian Link to comment Share on other sites More sharing options...
JohnA Posted November 7, 2005 Share Posted November 7, 2005 If you were to use a blowtorch on the boost pipe (theoretical example!) you could see 1.5bar boost at those revs. Keep the torch heating things up and you could see 2bar boost. That won't make the car any more powerful, needless to say, lol.... Just because the static pressure is higher, it doesn't mean that more air molecules get in the engine (which is what you really need in order to match the extra fuel) Link to comment Share on other sites More sharing options...
dangerous brain Posted November 7, 2005 Share Posted November 7, 2005 Thats why my power began to drop away after 1.15 bar. I really ought to tune the boost controller to 1.15 instead of 1.2 bar as it would drop my EGT's a little bit (every little counts) Link to comment Share on other sites More sharing options...
Ian C Posted November 7, 2005 Share Posted November 7, 2005 Can you tune it based on revs? Drop the boost as the revs get higher to de-stress the turbos. -Ian Link to comment Share on other sites More sharing options...
dangerous brain Posted November 7, 2005 Share Posted November 7, 2005 Its a blitz DSBC which in itself is as complicated with cack instructions as it gets so I have no idea if its tunable or even if I would want to attempt it lol. I did ask about det at the top end and the thor crew said they didn't detect any. The fact that I run iridium spark plugs and they haven't fallen apart yet supports this a bit. If the water injection reservoir runs out or I put sainsburies SUL in the car feels a bag of pants and can backfire on me if I gun it. Link to comment Share on other sites More sharing options...
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