czy18e Posted July 3, 2015 Share Posted July 3, 2015 I am currently running a 48mm progate and since fitting the 6870 it will not hold boost at the track. It held it on the dyno with slight creep after 6000rpm but at the track I'm hitting boost cut in first no matter how low I set the eboost. Has anyone done the straight swap for a 50mm? Will it hold it ya reckon? Or will I have to get a 60mm and do a cut and shut job on the exhaust manifold? Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/ Share on other sites More sharing options...
KiwiRS4T Posted July 3, 2015 Share Posted July 3, 2015 Not enough information . What engine? Have you got a boost chart? What power are you making? What spring do you have in the wastegate? What kind of dump? Pics? What is your boost cut set at? What ecu? Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7561989 Share on other sites More sharing options...
czy18e Posted July 3, 2015 Author Share Posted July 3, 2015 Rb25 650hp before it breaks down at 7200rpm (revs to 8000) Boost cut is set at 32psi 4" dump front wheel exit Ems computer 14psi spring No boost chart. Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7562020 Share on other sites More sharing options...
czy18e Posted July 3, 2015 Author Share Posted July 3, 2015 Want it to hold 30psi for 700hp (on dyno we had it set at 28 and it crept late then ignition break down at 7200)but as stated at the track I had it set 20 points lower on the eboost and it still hit 32psi as soon as it could in first gear. 60ft in 1.34. Was like a boost line was off. Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7562021 Share on other sites More sharing options...
KiwiRS4T Posted July 4, 2015 Share Posted July 4, 2015 Try a much stronger spring first - as near as possible to target boost is better. Set your boost cut a bit higher. Does it overboost in the other gears (apart from 1st)? If you can borrow a 50mm W/G that would be worth a try but if you have to buy one I would go straight to 60mm. Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7562108 Share on other sites More sharing options...
scotty nm35 Posted July 4, 2015 Share Posted July 4, 2015 If a boost line was off it may have hit over 60psi, mine did. Not sure about the gate you have, but Turbosmart had to re-design their spring caps to hold that boost. They made a much taller cap with springs 3 times as long, so the stiffer springs wouldn't limit the travel of the gate. If you hit the soft limit at the track, that would cause overboosting no matter what the controller was set to. Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7562133 Share on other sites More sharing options...
jet_r31 Posted July 4, 2015 Share Posted July 4, 2015 probally no point f**king around, just get a 60mm cheers darren Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7562171 Share on other sites More sharing options...
czy18e Posted July 4, 2015 Author Share Posted July 4, 2015 Interesting Scotty that sounds promising for the 50. Jet I would just get the 60 but it's a manifold off job, which I will do if I have to but I'm sure ive read plenty of people having success with the 50 so just chasing feedback. So easy to just bolt the 50 on and go racing. 60 is a major for me at the moment. Thanks for the feedback. Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7562260 Share on other sites More sharing options...
jay-rod Posted July 4, 2015 Share Posted July 4, 2015 My mate had same problem at near 570hp at rear wheel on a rb25/30He had a 48mm gate, had troubles with boost spikes not holding.Swapped it out for a 60mm and fixed the problem right up. Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7562350 Share on other sites More sharing options...
scotty nm35 Posted July 6, 2015 Share Posted July 6, 2015 The gate angle must be really crappy. 1 Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7563064 Share on other sites More sharing options...
czy18e Posted July 6, 2015 Author Share Posted July 6, 2015 It is twin scroll with two pipes feeding into the single gate flange. Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7563245 Share on other sites More sharing options...
Ben C34 Posted July 6, 2015 Share Posted July 6, 2015 Problem found. Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7563264 Share on other sites More sharing options...
iruvyouskyrine Posted July 6, 2015 Share Posted July 6, 2015 Why people have a split pulse manifold and share a gate is absolutely beyond me. Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7563269 Share on other sites More sharing options...
czy18e Posted July 6, 2015 Author Share Posted July 6, 2015 Bugger. So just never been a problem before because ball bearing Garrett not as efficient as precision or is it the size of the 6870? It controlled boost perfectly for 9 years with the old turbo. Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7563334 Share on other sites More sharing options...
czy18e Posted July 6, 2015 Author Share Posted July 6, 2015 Ok how about if I come With a possible solution. What if I keep the 48 in its current location and weld one of these 35psi jobs to the turbine housing? Or should I just cap off the original and weld the 48 to the turbine housing? Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7563381 Share on other sites More sharing options...
Ben C34 Posted July 6, 2015 Share Posted July 6, 2015 cap original. Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7563403 Share on other sites More sharing options...
czy18e Posted July 6, 2015 Author Share Posted July 6, 2015 Copy that. Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7563427 Share on other sites More sharing options...
Dose Pipe Sutututu Posted July 6, 2015 Share Posted July 6, 2015 more springs Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7563442 Share on other sites More sharing options...
czy18e Posted July 7, 2015 Author Share Posted July 7, 2015 How would more springs do anything beneficial? I have over boost problems. Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7563962 Share on other sites More sharing options...
scotty nm35 Posted July 7, 2015 Share Posted July 7, 2015 Over boosting isn't really an issue is it? Gate off the housing would be the go. Make sure it flows in the direction the gasses are traveling, not backwards like that manifold. Link to comment https://www.sau.com.au/forums/topic/457965-48mm-vs-50mm/#findComment-7564149 Share on other sites More sharing options...
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