Does Porting cause Slower Turbo Spool? FD / Twins Related
01-13-14, 08:20 AM
#1
Does Porting cause Slower Turbo Spool? FD / Twins Related
Alright I had a thread on the General rotary tech section , But since its not really a rotary problem I figured maybe here would be a better location
I've got a ported motor street ported , but i guess it was a bit more then I bargained for . it also has racing beat housings with a racing beat street exhaust port .
my vacuum is at 12 inches at 875
My problem is I have slow spool of the primary turbo on my sequentials Like everyone I assume its something wrong with the vacuum system . I went one by one replacing solenoids checking everything . and No problems
Disconnected the Pre control , and it did the same thing ,
VIdeo'd the turbo control working just fine when hot , when cold
disconnected the boost solenoid to check if that was getting overwhelmed and still same issues no changes .
12 psi is the most the car makes and its not instant it gradually raises until it hits 12 right befor the transition
I've tripple checked for boost leaks .
and after the transition its solid 14 psi until redline
So since the sequential turbo system itself is working . my question is what isnt.
What could be causing the primary to not boost as fast as it used to??
could it be that along with loss of low end torque and power porting also lessens the spool ?
Some info I forgot to include is the turbos hit 10 PSI over and the car gains some power at 2800 rpms
I've got a ported motor street ported , but i guess it was a bit more then I bargained for . it also has racing beat housings with a racing beat street exhaust port .
my vacuum is at 12 inches at 875
My problem is I have slow spool of the primary turbo on my sequentials Like everyone I assume its something wrong with the vacuum system . I went one by one replacing solenoids checking everything . and No problems
Disconnected the Pre control , and it did the same thing ,
VIdeo'd the turbo control working just fine when hot , when cold
disconnected the boost solenoid to check if that was getting overwhelmed and still same issues no changes .
12 psi is the most the car makes and its not instant it gradually raises until it hits 12 right befor the transition
I've tripple checked for boost leaks .
and after the transition its solid 14 psi until redline
So since the sequential turbo system itself is working . my question is what isnt.
What could be causing the primary to not boost as fast as it used to??
could it be that along with loss of low end torque and power porting also lessens the spool ?
Some info I forgot to include is the turbos hit 10 PSI over and the car gains some power at 2800 rpms
Last edited by Tem120; 01-13-14 at 08:42 AM.
01-13-14, 11:47 AM
#2
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porting could cause a slower turbo spool.
just generally, a later intake port closing time will move the powerband UP in the RPM range, this means also that the engine generally will loose power in the low rpm range, this could effect turbo spool.
an earlier opening intake port should help low rpm power.
an earlier opening exhaust port on a rotary hurts the BSFC of the engine, as it opens too early, before the combustion process is finished. this is pretty well documented SAE papers and books. it is possible that opening the exhaust earlier, helps turbo spool, as it is thought that the unburned gasses combust in the turbo (like a jet).
exhaust closing shouldn't do much except add overlap, which is probably worse than having a bigger port.
just generally, a later intake port closing time will move the powerband UP in the RPM range, this means also that the engine generally will loose power in the low rpm range, this could effect turbo spool.
an earlier opening intake port should help low rpm power.
an earlier opening exhaust port on a rotary hurts the BSFC of the engine, as it opens too early, before the combustion process is finished. this is pretty well documented SAE papers and books. it is possible that opening the exhaust earlier, helps turbo spool, as it is thought that the unburned gasses combust in the turbo (like a jet).
exhaust closing shouldn't do much except add overlap, which is probably worse than having a bigger port.
01-13-14, 12:33 PM
#3
porting could cause a slower turbo spool.
just generally, a later intake port closing time will move the powerband UP in the RPM range, this means also that the engine generally will loose power in the low rpm range, this could effect turbo spool.
an earlier opening intake port should help low rpm power.
an earlier opening exhaust port on a rotary hurts the BSFC of the engine, as it opens too early, before the combustion process is finished. this is pretty well documented SAE papers and books. it is possible that opening the exhaust earlier, helps turbo spool, as it is thought that the unburned gasses combust in the turbo (like a jet).
exhaust closing shouldn't do much except add overlap, which is probably worse than having a bigger port.
just generally, a later intake port closing time will move the powerband UP in the RPM range, this means also that the engine generally will loose power in the low rpm range, this could effect turbo spool.
an earlier opening intake port should help low rpm power.
an earlier opening exhaust port on a rotary hurts the BSFC of the engine, as it opens too early, before the combustion process is finished. this is pretty well documented SAE papers and books. it is possible that opening the exhaust earlier, helps turbo spool, as it is thought that the unburned gasses combust in the turbo (like a jet).
exhaust closing shouldn't do much except add overlap, which is probably worse than having a bigger port.
the exhaust ports were done by racing beat I bought the housings used though ...
wasn't exactly by my design LOL and top end power the car feels Extremly good . But low , and mid range gone dead none existant LOL
I guess I'll have to look up what benefits having later closing exhaust port does .
I will post a picture of the ports later as i'm really not all that knowledgeable regarding the Timing of the ports But Thank you for the reply atleast I can stop going crazying trying to figure out whats wrong .
Last edited by Tem120; 01-13-14 at 12:39 PM.
01-13-14, 04:33 PM
#4
Don't forget that a larger port will generally have slower velocity through it as it has more area. That's why it's hurting you in the low range. It's the complete opposite of how a velocity stack works. Those have large openings tapering down to a more narrow passage. This speeds up the flow. Your large port only allows for more total volume which lower back pressure in the top end.
Now I'm sure there are ways to improve apon this. There was a sequential turbo making 330rwhp that spoiled stupid fast. I can't remember it the exhaust was ported or not. I know you can increase spool with timing.
Now I'm sure there are ways to improve apon this. There was a sequential turbo making 330rwhp that spoiled stupid fast. I can't remember it the exhaust was ported or not. I know you can increase spool with timing.
01-13-14, 06:47 PM
#5
i vaguely remember a thread in which Aaron Cake spoke on porting and spool. maybe play around with the advanced search using his name and some of the key words from your topic - see if you can find it.
this is my thread on porting. nothing too heavy in it as it is geared mostly for new members, but posts 6 and 15 may be of interest to you.
https://www.rx7club.com/new-member-r...rimer-1039179/
will be interested in seeing your photos of the ports.
Last edited by diabolical1; 01-13-14 at 06:51 PM.
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01-15-14, 08:50 AM
#12
the ports ... (and keep in mind, this is just MY opinion) ...
the secondaries don't appear to be TOO aggressive. they look like a reasonable size to me. honestly, for me, i probably would have at least opened the primaries a bit earlier, but i do understand the reasoning behind leaving them stock. it's food for a good debate.
the exhausts are a bit puzzling to me. i can't really get a good sense of the closing edge and bevel, etc. question: i noticed you actually referred to them as "Racing Beat housings", is that to say they actually did the work, or are you just saying their template was used? i ask because they look pretty big for what i've come to expect in a "streetable" RB exhaust port - at least, they do in the photos.
the secondaries don't appear to be TOO aggressive. they look like a reasonable size to me. honestly, for me, i probably would have at least opened the primaries a bit earlier, but i do understand the reasoning behind leaving them stock. it's food for a good debate.
the exhausts are a bit puzzling to me. i can't really get a good sense of the closing edge and bevel, etc. question: i noticed you actually referred to them as "Racing Beat housings", is that to say they actually did the work, or are you just saying their template was used? i ask because they look pretty big for what i've come to expect in a "streetable" RB exhaust port - at least, they do in the photos.
01-15-14, 08:59 AM
#13
the ports ... (and keep in mind, this is just MY opinion) ...
the secondaries don't appear to be TOO aggressive. they look like a reasonable size to me. honestly, for me, i probably would have at least opened the primaries a bit earlier, but i do understand the reasoning behind leaving them stock. it's food for a good debate.
the exhausts are a bit puzzling to me. i can't really get a good sense of the closing edge and bevel, etc. question: i noticed you actually referred to them as "Racing Beat housings", is that to say they actually did the work, or are you just saying their template was used? i ask because they look pretty big for what i've come to expect in a "streetable" RB exhaust port - at least, they do in the photos.
the secondaries don't appear to be TOO aggressive. they look like a reasonable size to me. honestly, for me, i probably would have at least opened the primaries a bit earlier, but i do understand the reasoning behind leaving them stock. it's food for a good debate.
the exhausts are a bit puzzling to me. i can't really get a good sense of the closing edge and bevel, etc. question: i noticed you actually referred to them as "Racing Beat housings", is that to say they actually did the work, or are you just saying their template was used? i ask because they look pretty big for what i've come to expect in a "streetable" RB exhaust port - at least, they do in the photos.
01-15-14, 10:02 AM
#18
I'm sorry I haven't been able to test one of my FDs to give you exact rpm I hit full boost on primary but it definitely shouldn't be gradual unless you have creep. When I set the primary to 10, 12 or 14psi it happens near instantly. No gradual climb to hit the target boost. A good video of your boost gauge on a 3rd gear pull would show a lot.
I should be able to do the test on Friday for you.
I should be able to do the test on Friday for you.
01-15-14, 10:07 AM
#19
I'm sorry I haven't been able to test one of my FDs to give you exact rpm I hit full boost on primary but it definitely shouldn't be gradual unless you have creep. When I set the primary to 10, 12 or 14psi it happens near instantly. No gradual climb to hit the target boost. A good video of your boost gauge on a 3rd gear pull would show a lot.
I should be able to do the test on Friday for you.
I should be able to do the test on Friday for you.
Will do I'll see about getting that video ,
and no problem on not being able to test it out . I'm gonna check for a boost vacume leak again . I'd jump for joy if i could find one LOL
Last edited by Tem120; 01-15-14 at 10:20 AM.
01-15-14, 10:29 AM
#20
Tem120, intentional or not, i think someone duped you with those rotor housings.
i wouldn't feel comfortable declaring that the exhaust ports are the cause of your spool issues, but my guess is they aren't doing you any favors.
01-15-14, 11:01 AM
#22
i agree. that doesn't even look like their race port template. they bare a resemblance to the Pineapple template though, but as i said, i can't see detail of the closing edge.
Tem120, intentional or not, i think someone duped you with those rotor housings.
i wouldn't feel comfortable declaring that the exhaust ports are the cause of your spool issues, but my guess is they aren't doing you any favors.
Tem120, intentional or not, i think someone duped you with those rotor housings.
i wouldn't feel comfortable declaring that the exhaust ports are the cause of your spool issues, but my guess is they aren't doing you any favors.
But well since this is what it is . What else could be causing the slow Spool .
I'm gonna try and do that 3rd gear pull today after work . I will only do a pull to maybe 4k
Last edited by Tem120; 01-15-14 at 11:07 AM.
