Overboosting or normal...
12-12-10, 06:01 PM
#1
Exhaust Leak Fixed
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Overboosting or normal...
ok.. so i have an 89 vert with a jdm tII swap in it. ive had it running for two days now and im getting a little concerned with how much power it has for a relatively stock setup. dont get me wrong i love the power that it has i am just not sure if its safe for the car. im pretty sure that im running an unchipped n370 ecu, 3inch corksport DP, 3 inch midpipe, and 2.5 inch duel racing beat mufflers with a 3 inch intake. i dont know that it makes much difference but im using an n390(Fd) recirculation valve and it is recirculating..no open atmosphere. but anyways im getting around 10psi peak boost in 1st and 2nd and 12psi peak boost in 3rd and 4th. i do not have aN FCD and i cant tell if im actually hitting the fuel cut.. i assume that hitting the fuel cut is a noticeable thing. Also i do have a narrow band O2 sensor (yes i know they are inaccurate) and it always halfway into Rich on a hard pull. so do i need to keep my foot out of it. i need this engine to last me for at least 2 years.. not doing any other mods to it for quite some time. but anywho... let me know what you guys think
12-12-10, 07:58 PM
#4
If you overboost and it is in fact an unchipped ecu you'll definately know it. I would suggest cracking the ecu open to see if it has been chipped or not. My S5 JDM swap (n370 ecu, the n374 didn't agree with my car), without a boost controller hit fuel cut at 11 psi boost. If you are reaching 12 psi and not "hitting a wall" then I would suspect a modded ecu. I would highly recommend a boost controller (manual one's work fine and they can be sourced for around $15.00)
12-12-10, 10:00 PM
#6
i would lay off the throttle until you can get the car tested with a wideband to see if it is actually safe AFR wise, not knowing anything about the ECU or fuel system. i'm sure it has some mods like 720 secondaries but i still bet your running on borrowed time if you continue pushing it.
12-13-10, 12:27 AM
#7
10-12 psi is not at all safe with a stock fuel system. The stock TII fuel pump's flow takes a nosedive once you push it past its normal pressure levels, and 550cc primaries max out before the secondaries can come online at 3800. Combine those 2 factors, and you'll get a nasty lean spot right where the engine is making peak torque & boost. I made a thread in the Rtek section after I found my own primaries maxing out: https://www.rx7club.com/rtek-forum-168/secondary-staging-issue-844350/.
And fuel cut is supposed to be at 8.6 psi, so you're somehow skipping it.
And fuel cut is supposed to be at 8.6 psi, so you're somehow skipping it.
Last edited by RotaryRocket88; 12-13-10 at 12:33 AM.
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12-13-10, 02:52 PM
#9
Exhaust Leak Fixed
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If i do infact have a modded ECU do i still need to purchase an FCD. also i thought that it was just the S4s that had the boost creep issue. and how much power can a OEM clutch handle. i seems as though the clutch that came with my jdm engine starts slipping when i hit 12-14 psi boost. i could tell that the clutch had been used but there was bearly any wear on it.
12-13-10, 03:29 PM
#10
Exhaust Leak Fixed
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i have another question... if i were to just run a vacuum line straight to the waist gate and not use the turbo duty solenoid would the waste gate open at 5psi boost since the WG has a 5 pound spring. if i could cap my boost at 5 psi for the time being i would feel more comfortable
12-13-10, 03:39 PM
#11
the solenoids only purpose is to spool the turbo quicker then it shuts fully to let the wastegate manage boost on its own, disconnecting it will only make the turbo laggier but not affect the creep.
the car is hitting higher boost levels because you have free flowing intake and exhaust, put back in the stock air box and main cat and it should be back down to near stock, safe, boost levels.
there is something already getting rid of boost cut if your boost gauge is accurate, it should be hitting boost cut at 8.6psi and it's not something you would easily miss.
the stock clutch is good for anywhere from 250whp to 350ish, but if your clutch is old then the springs are likely tired. it also depends how the clutch was broken in and if the flywheel is glazed or not. my aftermarket cheapo OEM clutch grips perfectly fine even at 325-350WHP levels. so your clutch is probably old and tired.
the car is hitting higher boost levels because you have free flowing intake and exhaust, put back in the stock air box and main cat and it should be back down to near stock, safe, boost levels.
there is something already getting rid of boost cut if your boost gauge is accurate, it should be hitting boost cut at 8.6psi and it's not something you would easily miss.
the stock clutch is good for anywhere from 250whp to 350ish, but if your clutch is old then the springs are likely tired. it also depends how the clutch was broken in and if the flywheel is glazed or not. my aftermarket cheapo OEM clutch grips perfectly fine even at 325-350WHP levels. so your clutch is probably old and tired.
12-13-10, 04:00 PM
#12
Exhaust Leak Fixed
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the solenoids only purpose is to spool the turbo quicker then it shuts fully to let the wastegate manage boost on its own, disconnecting it will only make the turbo laggier but not affect the creep.
the car is hitting higher boost levels because you have free flowing intake and exhaust, put back in the stock air box and main cat and it should be back down to near stock, safe, boost levels.
there is something already getting rid of boost cut if your boost gauge is accurate, it should be hitting boost cut at 8.6psi and it's not something you would easily miss.
the stock clutch is good for anywhere from 250whp to 350ish, but if your clutch is old then the springs are likely tired. it also depends how the clutch was broken in and if the flywheel is glazed or not. my aftermarket cheapo OEM clutch grips perfectly fine even at 325-350WHP levels. so your clutch is probably old and tired.
the car is hitting higher boost levels because you have free flowing intake and exhaust, put back in the stock air box and main cat and it should be back down to near stock, safe, boost levels.
there is something already getting rid of boost cut if your boost gauge is accurate, it should be hitting boost cut at 8.6psi and it's not something you would easily miss.
the stock clutch is good for anywhere from 250whp to 350ish, but if your clutch is old then the springs are likely tired. it also depends how the clutch was broken in and if the flywheel is glazed or not. my aftermarket cheapo OEM clutch grips perfectly fine even at 325-350WHP levels. so your clutch is probably old and tired.
unfortunately i do not have a stock air box and i also do not have stock exhaust to replace mine with. will porting my waist gate eliminate this boost creep or at least reduce it by alot.
Like i said before i NEED this engine to last me so what ever i need to do to keep it running as long as possible i need to do. starting with keeping my foot out of the gas pedal.
12-13-10, 04:11 PM
#13
Exhaust Leak Fixed
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i just spoke with the guy i bought the ecu from and he said and i quote "My car was pushing a steady 10th psi,I also didn't have a fuel cut defense and never got fuel cut off.maybe cause I was using the n/a harness modified."
12-13-10, 04:27 PM
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Exhaust Leak Fixed
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>>>>edit. i found a thread for the s4.. is that the same process.. how big do i need to port the waste gate. ive ported one for an FD before using the faq from rotary resurrection.. should i do the same thing. he said to use spray paint and paint over the waste gate flapper and then lift flapper and port the unpainted inner ring. does that sound about right for the s5 as well
12-13-10, 04:42 PM
#16
http://fc3spro.com/TECH/HOWTO/KWG/kwg.html
There will probably be a circle made around the flapper from carbon deposits, but you can use paint or a scribe to mark it. Don't port too close to the edge of the flapper, or it will leak at all times & hurt spool up. Try to leave 1-2mm on the edges. I ported my wastegate ports out to 23mm and 26mm, which gives the equivalent area of a single 35mm port. End result is 25% more area than stock, and no boost creep with a 3" TID and 2.5" exhaust.
There will probably be a circle made around the flapper from carbon deposits, but you can use paint or a scribe to mark it. Don't port too close to the edge of the flapper, or it will leak at all times & hurt spool up. Try to leave 1-2mm on the edges. I ported my wastegate ports out to 23mm and 26mm, which gives the equivalent area of a single 35mm port. End result is 25% more area than stock, and no boost creep with a 3" TID and 2.5" exhaust.
12-13-10, 05:11 PM
#20
I would not try that. You'll ruin the housing by breaking down the wall separating the two runners, and you would have to modify the flapper to seal properly. It's an oval door with 2 circular sections that stick out and seal against the ports. If you just shaved the surface down, the door would probably sit at an angle and leak.
Just port the openings, and back cut down to the runners with a carbide burr. A dremel will take forever to port it.
Just port the openings, and back cut down to the runners with a carbide burr. A dremel will take forever to port it.
12-13-10, 05:16 PM
#21
Exhaust Leak Fixed
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haha.. i wansnt planning on actually doing that. just cuirous if anyone had done it before. at first glance it looked like it would be a better way to port it. how hard is it to actually remove the turbo
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