As long as the cold pipe is smaller or the same diameter as the hot pipe then there shouldn't be any pressure drop from a larger IC core.
Intercooler and boost question
- Thread starter MShreve
- Start date
As long as the cold pipe is smaller or the same diameter as the hot pipe then there shouldn't be any pressure drop from a larger IC core.
- :
- 2007 Mazdaspeed 6 Sport
Are you sure you wouldn't take some degree of pressure drop at the exit of the hot pipe into the intercooler? If the intercooler is larger, the volume of allowance for the pressure drop would be greater.
SMOKEYS36SHOP
Member
- :
- 2007 Mazdaspeed 6
ok...i am confused now lol...how does any of this have anything to do with why 2 members of this community are boosting almost 5 lbs higher than i am? i thought the tmic helps hold boost better gaining almost 2 lbs of boost from a tmic ? thats what started this whole topic . mshreve has a similar setup as i do except he has a test pipe and a bpv and i dont. i have a hybrid bov. how is he spiking to 20? i have never had that happen lol the most is 17.5 for a second and its right down to 15. when i called mark at su yesterday he said that the ms6 stock computer is set up to always hold at 15.5 lbs of boost and said that anything more would require a boost controller or computer...idk this weekend i am going to retighten all my clamps. i plan on getting my test pipe in 2 weeks and after i install it we will see how my boost levels are. i mean maybe because i have this hybrid bov its not holding boost well..idk
Well maybe its your BOV but I would say as long as your holding 15 lbs your fine. To be honest my car will hold anywhere from 15.6-19 psi depending on temp / humidity / car. I spike around 20-21 tops. Im not too familiar with the hybrid so I don't really know much. Your running recirc right? I think they test pipe will bump your boost levels a bit. That seems to be the common denominator. Stock exhaust is very restrictive.
SMOKEYS36SHOP
Member
- :
- 2007 Mazdaspeed 6
so coyfish do you have the cobb ap yet?
and no my turboxs hybrid bov is a 50/50 blend doing both atmospheric and recirculate
and no my turboxs hybrid bov is a 50/50 blend doing both atmospheric and recirculate
Ok folks. The gauge indicated boost is the pressure value relative to the ambient pressure at the gauge. The pressure in the manifold is absolute pressure. The ECU will operate the wastegate to hit the absolute pressure target value in the manifold. Near sea-level the gauge indication and absolute are very close to equal. At higher altitudes, the ambient pressure is significantly lower, so the indicated boost will be higher because the turbo must "blow" harder at the lower ambient pressure to hit the absolute pressure value. If your ion the coast of Florida at WOT, your boost gauge should read lower than the same car WOT in Denver.... This action also explains why your car will indicate different boost values on different days. If there is a high pressure front in your area, the indicated boost will be lower than on a low pressure front day. Sunny hot day, lower "indicated" boost, cloudy rainy day higher "indicated" boost. The abolute pressure (MAP) in the manifold is the SAME. Get it?
all4bspinnin
Member
- :
- 2006 Mazdaspeed 6
for the record, a boost spike can be very dangerous for the motor... it only takes one good detonation event to bust a piston. This thread is a great example of why external wastegates are such a good idea
SMOKEYS36SHOP
Member
- :
- 2007 Mazdaspeed 6
ok forzda i understand what your saying but and i cant speak for the elevation of mshreve in Oregon but here in new york i am very close to sea level and i am sure coyfish is about the same because most of florida is flat lol. but it still doesnt change why his boost levels are much higher than mine. and again i dont think coyfish has a cobb ap so i cant see why his is 5 lbs higher than mine when it comes to boost...also i cant see even someone in oregon having the same 5 lbs increase in boost even at such a higher altitude when the computer is supposed to hold boost at 15.5. i mean what about the theory of overboosting and hitting boost cut? i mean our cars should hit a wall at around 18 lbs of boost without some kind of Boost Cut Defender or computer? i dont get it one bit
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- 2007 Mazdaspeed 6 Sport
In short, what Forzda has explained means that what your boost gauge says is simply how hard the turbo is working and not necessarily the true boost pressure. The boost gauge and what it indicates do not correct for environmental changes.
Thank you, Forzda.
SMOKEYS36SHOP
Member
- :
- 2007 Mazdaspeed 6
i wish someone local had a forge bpv to try to see if my bov is the problem or not...putting on my stock bpv sucks...in fact it leaked so much that my boost levels in first and second gear was only 8 pounds before changing it out to the turboxs...im frustrated lol. i can understand the whole thing with the environment changes but right now in new york its beautiful with a high of 72 right now with no humidity and it doesn't change my boost levels on days that it rains and is nasty and humid...idk. i hate to keep bitching about it but i am not coming up with anything that is clear cut about this topic. its just frustrating to hear other people with such high amounts of boost like that on the stock computer. i dont get it
Your gauges are incorrect. Many are. You must check them with a verified source to be sure of their accuracy. I have a large 4" diameter fuel pressure
tester that is calibrated to within 1/4 lb. You can get them fairly cheaply at auto parts tool sections. The best comparison is at idle. What is the vacuum at idle. If they are not IDENTICAL, the indicated boost WILL be different and maybe significantly.
Looks like a normal log to me. The initial spike is because it takes "some" amount of time for the ECU to see the boost coming up very quickly, open the WG Sol so the boost pressure can be applied to the WGA, then the mechanical WGA must open the flapper, then some of the exhaust bypasses the turbine, the turbine slows down and the boost tapers off to the actual setting desired. Check the timing in the log. This action took 4/10 (0.4) sec and all is well. If you roll into the throttle a bit more gently, the boost will only rise to the ~15-16 psi. Like I said, it's normal and well documented in several of the related forums.
I would expect the indicated boost (boost gauge, not DH reading) to be somewhat higher at higher elevations(lower ambient pressure). If any are really a nit-picker and inclined to work the math, you can estimate what the boost difference would be based on the sea-level numbers and the absolute pressure in the manifold as measured by the MAP sensor....
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