Took 1st in NASA TT1 - Electric Vacuum Pump question
Jun 11, 2018, 04:09 PM
#16
This is odd, I've NEVER had this happen in over a decade of tracking Evos. Of course I am smart enough to know that even if it hasn't happened to me doesn't mean it can't happen.
The track I frequent I hit 134mph down the front straight and it's full WOT from 3rd to 5th gear @ over 500whp. Never once had this problem with my current Evo 10 or my Evo 8 before.
This can't be normal. Sounds like a possible fault in the system.
The track I frequent I hit 134mph down the front straight and it's full WOT from 3rd to 5th gear @ over 500whp. Never once had this problem with my current Evo 10 or my Evo 8 before.
This can't be normal. Sounds like a possible fault in the system.
Jun 12, 2018, 03:58 AM
#17
It’s got me wondering too if it’s my brake system. I’m on FP Red JB over 28psi, GSC 2 cams, stage V head, etc. The way it’s behaving just seems like vacuum. I haven’t been able to hit brakes after full boost in years. I miss the ability to hit the brakes and immediately slow down.
If it’s a system fault, where can I check after confirming it’s not the check valve? Assuming because nobody else has had this problem, I don’t think I am over powering the check valve. But who knows, I seem to uncover all kinds of “firsts”. LOL.
I thought some of you would have added an electric vacuum pump or larger reservoir?
If it’s a system fault, where can I check after confirming it’s not the check valve? Assuming because nobody else has had this problem, I don’t think I am over powering the check valve. But who knows, I seem to uncover all kinds of “firsts”. LOL.
I thought some of you would have added an electric vacuum pump or larger reservoir?
Jun 12, 2018, 09:23 AM
#19
It’s got me wondering too if it’s my brake system. I’m on FP Red JB over 28psi, GSC 2 cams, stage V head, etc. The way it’s behaving just seems like vacuum. I haven’t been able to hit brakes after full boost in years. I miss the ability to hit the brakes and immediately slow down.
If it’s a system fault, where can I check after confirming it’s not the check valve? Assuming because nobody else has had this problem, I don’t think I am over powering the check valve. But who knows, I seem to uncover all kinds of “firsts”. LOL.
I thought some of you would have added an electric vacuum pump or larger reservoir?
If it’s a system fault, where can I check after confirming it’s not the check valve? Assuming because nobody else has had this problem, I don’t think I am over powering the check valve. But who knows, I seem to uncover all kinds of “firsts”. LOL.
I thought some of you would have added an electric vacuum pump or larger reservoir?
I wouldn't suppose you have a brake booster to swap in and test...?
Oh, and congrats on the win, dude!
Jun 12, 2018, 03:39 PM
#21
this is not really the same but when i had large cams in my firebird it didn't make enough vacuum, only about 8inHg at idle, for the brakes to work right and be safe on the road. all i did to solve this problem was to run a separate vacuum canister in line with the brake booster that would store vacuum. So when decel or anytime vacuum is high the canister will store vacuum for when you need brakes
Jun 13, 2018, 07:13 AM
#23
It's an old topic but now this has grown into two topics, thanks kyoo lol.
RPM hang - in my experience this has been resolved in the tune itself across several different tuners over the years. What table it is I've no idea but that's the fix. What is it? This is after long full boost straights which I almost exclusively have down here in the southeast, sitting around 130-150mph (with less then 400hp) and you lift to go to braking the RPM STAYS and does not drop for a couple of seconds. No clutch action, just lifting.
No vac on brake booster - VERY common since we've been tracking these things. In a 10/10 lap you normally would go from gas to brakes in a couple of milliseconds, at the last second. However when you do this there is still boost or positive pressure in the valve cover for those ~2 seconds, aka no vac on booster, aka rock hard pedal. Your valve cover does not have a blow off valve to instantly dump that, and most of you do not have dry sumps to assist it. If you take a "1 one thousand" to go from gas to brake then you likely would not experience this very often and certainly not on medium straights. My non-boosted cars never have this issue. P-cars don't either because of clever design. Remember we have a 4 door grocery getter brake booster designed to pull into your driveway. Some guys who've gone full pedal box / manual brakes don't see this either naturally. Since I've been road racing I can change my line to adjust for it around certain braking zones to prevent the vette's and such from out braking me, but yes it's always been a problem.
RPM hang - in my experience this has been resolved in the tune itself across several different tuners over the years. What table it is I've no idea but that's the fix. What is it? This is after long full boost straights which I almost exclusively have down here in the southeast, sitting around 130-150mph (with less then 400hp) and you lift to go to braking the RPM STAYS and does not drop for a couple of seconds. No clutch action, just lifting.
No vac on brake booster - VERY common since we've been tracking these things. In a 10/10 lap you normally would go from gas to brakes in a couple of milliseconds, at the last second. However when you do this there is still boost or positive pressure in the valve cover for those ~2 seconds, aka no vac on booster, aka rock hard pedal. Your valve cover does not have a blow off valve to instantly dump that, and most of you do not have dry sumps to assist it. If you take a "1 one thousand" to go from gas to brake then you likely would not experience this very often and certainly not on medium straights. My non-boosted cars never have this issue. P-cars don't either because of clever design. Remember we have a 4 door grocery getter brake booster designed to pull into your driveway. Some guys who've gone full pedal box / manual brakes don't see this either naturally. Since I've been road racing I can change my line to adjust for it around certain braking zones to prevent the vette's and such from out braking me, but yes it's always been a problem.
Jun 13, 2018, 07:50 AM
#24
It's an old topic but now this has grown into two topics, thanks kyoo lol.
RPM hang - in my experience this has been resolved in the tune itself across several different tuners over the years. What table it is I've no idea but that's the fix. What is it? This is after long full boost straights which I almost exclusively have down here in the southeast, sitting around 130-150mph (with less then 400hp) and you lift to go to braking the RPM STAYS and does not drop for a couple of seconds. No clutch action, just lifting.
No vac on brake booster - VERY common since we've been tracking these things. In a 10/10 lap you normally would go from gas to brakes in a couple of milliseconds, at the last second. However when you do this there is still boost or positive pressure in the valve cover for those ~2 seconds, aka no vac on booster, aka rock hard pedal. Your valve cover does not have a blow off valve to instantly dump that, and most of you do not have dry sumps to assist it. If you take a "1 one thousand" to go from gas to brake then you likely would not experience this very often and certainly not on medium straights. My non-boosted cars never have this issue. P-cars don't either because of clever design. Remember we have a 4 door grocery getter brake booster designed to pull into your driveway. Some guys who've gone full pedal box / manual brakes don't see this either naturally. Since I've been road racing I can change my line to adjust for it around certain braking zones to prevent the vette's and such from out braking me, but yes it's always been a problem.
RPM hang - in my experience this has been resolved in the tune itself across several different tuners over the years. What table it is I've no idea but that's the fix. What is it? This is after long full boost straights which I almost exclusively have down here in the southeast, sitting around 130-150mph (with less then 400hp) and you lift to go to braking the RPM STAYS and does not drop for a couple of seconds. No clutch action, just lifting.
No vac on brake booster - VERY common since we've been tracking these things. In a 10/10 lap you normally would go from gas to brakes in a couple of milliseconds, at the last second. However when you do this there is still boost or positive pressure in the valve cover for those ~2 seconds, aka no vac on booster, aka rock hard pedal. Your valve cover does not have a blow off valve to instantly dump that, and most of you do not have dry sumps to assist it. If you take a "1 one thousand" to go from gas to brake then you likely would not experience this very often and certainly not on medium straights. My non-boosted cars never have this issue. P-cars don't either because of clever design. Remember we have a 4 door grocery getter brake booster designed to pull into your driveway. Some guys who've gone full pedal box / manual brakes don't see this either naturally. Since I've been road racing I can change my line to adjust for it around certain braking zones to prevent the vette's and such from out braking me, but yes it's always been a problem.
Jun 13, 2018, 07:56 AM
#25
I had a lot of issues with RPM hang but only after the car got beyond normal driving hot. Like at the end of a dual driven AutoX session. The problem got worse and worse till it wasnt just a hang at high rpm but wouldnt always even come back to idle. In my case, the TB shaft was starting to stick. I just pulled off the TPS sensor and dropped some lube down there to free it up. I also blew the motor that weekend, so was able to pull it all apart and check nothing was bent/broken.
That seemed to be the fix for me, YMMV
That seemed to be the fix for me, YMMV
Jun 13, 2018, 08:43 AM
#27
ok hold on. now that I think about this, I think I have this too. I didn't think much of it at the time, but at the end of the main straight of autobahn south, I brake and it's initially "firm" before sinking down to where it really bites. I figured hot brakes or something like that, but it must be this vacuum thing? if revs are hanging you're not getting engine braking but that is separate from the actual brake function and pedal stiffness. or is it? are we getting the vacuum we need if revs are hanging longer than they should?
what do other evos do, and other question still holds - all other turbo cars in this class experience this?
what do other evos do, and other question still holds - all other turbo cars in this class experience this?
Jun 13, 2018, 10:33 AM
#28
It's an old topic but now this has grown into two topics, thanks kyoo lol.
RPM hang - in my experience this has been resolved in the tune itself across several different tuners over the years. What table it is I've no idea but that's the fix. What is it? This is after long full boost straights which I almost exclusively have down here in the southeast, sitting around 130-150mph (with less then 400hp) and you lift to go to braking the RPM STAYS and does not drop for a couple of seconds. No clutch action, just lifting.
No vac on brake booster - VERY common since we've been tracking these things. In a 10/10 lap you normally would go from gas to brakes in a couple of milliseconds, at the last second. However when you do this there is still boost or positive pressure in the valve cover for those ~2 seconds, aka no vac on booster, aka rock hard pedal. Your valve cover does not have a blow off valve to instantly dump that, and most of you do not have dry sumps to assist it. If you take a "1 one thousand" to go from gas to brake then you likely would not experience this very often and certainly not on medium straights. My non-boosted cars never have this issue. P-cars don't either because of clever design. Remember we have a 4 door grocery getter brake booster designed to pull into your driveway. Some guys who've gone full pedal box / manual brakes don't see this either naturally. Since I've been road racing I can change my line to adjust for it around certain braking zones to prevent the vette's and such from out braking me, but yes it's always been a problem.
RPM hang - in my experience this has been resolved in the tune itself across several different tuners over the years. What table it is I've no idea but that's the fix. What is it? This is after long full boost straights which I almost exclusively have down here in the southeast, sitting around 130-150mph (with less then 400hp) and you lift to go to braking the RPM STAYS and does not drop for a couple of seconds. No clutch action, just lifting.
No vac on brake booster - VERY common since we've been tracking these things. In a 10/10 lap you normally would go from gas to brakes in a couple of milliseconds, at the last second. However when you do this there is still boost or positive pressure in the valve cover for those ~2 seconds, aka no vac on booster, aka rock hard pedal. Your valve cover does not have a blow off valve to instantly dump that, and most of you do not have dry sumps to assist it. If you take a "1 one thousand" to go from gas to brake then you likely would not experience this very often and certainly not on medium straights. My non-boosted cars never have this issue. P-cars don't either because of clever design. Remember we have a 4 door grocery getter brake booster designed to pull into your driveway. Some guys who've gone full pedal box / manual brakes don't see this either naturally. Since I've been road racing I can change my line to adjust for it around certain braking zones to prevent the vette's and such from out braking me, but yes it's always been a problem.
As for the brakes I don't think I go from 100% throttle to an immediate brake. My rhythm takes some time to get from the gas over to the brake pedal, other than emergency situations. Even then, I've been really lucky.
Or maybe I've had these going on, got used to them and just don't notice? I'll be aware next time and see if I notice anything strange.
Jun 13, 2018, 11:10 AM
#29
That's nuts! I don't think I've ever had my car voluntarily stay on the gas. That would be some scary ****. For me it was always that weird thing Evos do when the RPMs don't want to come down between shifts, but the car was never accelerating, as the RPM would come down as soon as I let out the clutch. Your issue would just be downright scary. If it's shaft seals, as mentioned above, I did lube the heck out of mine when I put them in. Either way, what a pucker moment.
As for the brakes I don't think I go from 100% throttle to an immediate brake. My rhythm takes some time to get from the gas over to the brake pedal, other than emergency situations. Even then, I've been really lucky.
Or maybe I've had these going on, got used to them and just don't notice? I'll be aware next time and see if I notice anything strange.
As for the brakes I don't think I go from 100% throttle to an immediate brake. My rhythm takes some time to get from the gas over to the brake pedal, other than emergency situations. Even then, I've been really lucky.
Or maybe I've had these going on, got used to them and just don't notice? I'll be aware next time and see if I notice anything strange.
brake booster not getting vacuum quickly may be entirely separate. I've decided to get a new hose (which has check valve built in). it's like $36 bucks, why not. car's old.
Jun 13, 2018, 11:28 AM
#30
If I'm understanding right, he's letting off the gas and the RPM are staying up, not allowing engine braking. Air has to be getting in, somehow, to keep the engine going so basically the same affect as the car still being on the gas as the engine is still firing. I didn't know of another way to explain it LOL. He may not have the pedal down, but the car does
After reading Dallas' experience with the TB seals, that's kinda what I picture happening.
Unrelated, but I had something like this happen, once: I had my throttle cable too tight after putting the engine back in. I forget to set it. LOL. I was going down the street and the car would cruise at 3k RPM without my touching anything. I was like, "WWWWTTTFFF???!!" HAHA.
Depending on the RPM, this throttle hang may keep enough vacuum from building. I know my stock turbo keeps my car at or near zero psi/in.hg when I just look at it. If you are at crazy full boost, then the car is hanging the revs, I could definitely see the brakes acting up.
After reading Dallas' experience with the TB seals, that's kinda what I picture happening.
Unrelated, but I had something like this happen, once: I had my throttle cable too tight after putting the engine back in. I forget to set it. LOL. I was going down the street and the car would cruise at 3k RPM without my touching anything. I was like, "WWWWTTTFFF???!!" HAHA.
Depending on the RPM, this throttle hang may keep enough vacuum from building. I know my stock turbo keeps my car at or near zero psi/in.hg when I just look at it. If you are at crazy full boost, then the car is hanging the revs, I could definitely see the brakes acting up.