vacuum boost at idle

[CerberuSlol]

So not sure what happened but if I'm not mistaken my car was around -15-20 in hg at idle and now it just sits at 0. When you get on it still boosts fine and reads accurately but the actual vacuum seems off. We checked all the lines doesn't seem to be a leak but not sure. Is this ok to drive with until I sort it out?

[evildky]

Hook a vac gauge to the plenum at idle, if you aren't pulling vacum then your timing is way off, could also be a sender or gauge issue since I assume we're talking abotu the zr?

[CerberuSlol]

Yea this is with my rb25 200zr. I'm running all aftermarket mechanical autometer ultralite 2 gauges. Now we checked all the lines for holes/tears or kinks everything was fine in that regard. This time though when driving in 3rd and 4th it will climb boost and without letting off just goes down and then well quickly flash to possible said boost. I have noticed a loss of a power. Were going to run full boost leak test tonight or tomorrow. Only other thing I can think of is since my clutch was starting to go even though thats pretty damn new it needed to be bled and it was slipping now we bled the one slave cylinder valve but there is another one on top or whatever we didn't bleed that I got part of my clutch pedal back but it still has a bit too much play and is being noisy while going into gear. I've heard that the clutch can affect the boost while engine is under load so maybe it's something as simple as just bleeding that other cylinder. Not sure what else to do at this point other then that. It's at least underboosting and not over boosting but I'm not hitting near as much boost as I was and the gauge is acting funky the way it's reading.

[CerberuSlol]

Also after looking at it closer I'm guessing that thing I thought was another cylinder is just the clutch dampener?

[evildky]

We are talking about 2 different issues here, you car should pull vac at idle in neutral, the clutch has nothign to do with engine vacum. when you drive the car the vac will fluctuate up to zero then into boost depending on how much skinny pedal you're giving it, the less skinny pedal on the flatest surface will give you the most vac and the best fuel economy, the more skinny pedal, the steeper the grade the more boost you generate and the worse your fuel economy. a slipping clutch might limit how much boost you can make, and the more boost you make the faster you kill the clutch if it's slipping. When you bleed the hydraulics of the clutch you have to bleed the clutch damper as well as the slave, failure to do this could result in air int he line, the clutch nto fulley disengaging and bad things happeneing. The dampener can be bypassed usign a brake line from an S130 IIRC. I didn't think the jap cars came wiht dampners, i thought that was a US market thing?

[CerberuSlol]

We are talking about 2 different issues here, you car should pull vac at idle in neutral, the clutch has nothign to do with engine vacum. when you drive the car the vac will fluctuate up to zero then into boost depending on how much skinny pedal you're giving it, the less skinny pedal on the flatest surface will give you the most vac and the best fuel economy, the more skinny pedal, the steeper the grade the more boost you generate and the worse your fuel economy. a slipping clutch might limit how much boost you can make, and the more boost you make the faster you kill the clutch if it's slipping. When you bleed the hydraulics of the clutch you have to bleed the clutch damper as well as the slave, failure to do this could result in air int he line, the clutch nto fulley disengaging and bad things happeneing. The dampener can be bypassed usign a brake line from an S130 IIRC. I didn't think the jap cars came wiht dampners, i thought that was a US market thing?

Yea I know the clutch has nothing to do with engine in vaccum was only talking about it affecting the boost but I got you. We are going to bleed the dampener tonight and hopefully that helps. Also replacing a coupler that is between the turbo and the maf that is a little worn and may not be sealed all the way so that might be messing with my air fuel ratio. You can bleed the dampner the same way you would a slave right nothing special to do it?

[evildky]

Yup bleeds just like the slave.

[CerberuSlol]

Yea we bled that clutch is alot better, still have issue with the boost though there is a loss of power you can get on it full throttle and it will stay at almost full boost for like a few seconds then just significantly drop even down into vacuum and in lower gears it's not even boosting at times.

[CerberuSlol]

To be honest the one thing we didn't check was the blow off valve. Just thought of that going to do that tomorrow. Spring could be completely worn,or just not a good seal or something would explain alot of s***.

[CerberuSlol]

yea just found out after reading the greddy website for s***. I have a fake greddy bov so guessing when that spring was adjusted since it's a cheap pos it f*** with my s***. Just not sure how to go about fixing this now.

[CerberuSlol]

So just found out I have a fake greddy bov after using http://www.greddy.com/featured/25 to see. Pretty sure the spring f*** up inside of it and the seal wasn't complete causing a boost leak,idle and affecting my turbo response. Now question to you guys is do I just replace the bov with a real greddy/tial/hks or whatever. Or do I just fix the seal and replace the spring? Also pretty sure it's an atmospheric bov should I be running the recirculating ones?

[evildky]

yes you should be running a recirc type, an atmospheric type causes a rich condition every time if opens as the ecu measures air as it passes the afm. Many are convertible you simply unscrew the horn and screw in a hose nipple. I like Tial bov's but there are some nice stock donors available too.

[CerberuSlol]

s*** is confusing cause I contacted both mckinney motorsports and jim wolf and mckinney said it's not necessary but in some cases it does help with idle and less tendency to stall. Spoke to them on phone and email in the email jim wolf said

We do not advise using BOVs that vent to atmosphere on cars that run a MAF sensor based control system. We recommend using a compressor bypass valve or recirculation valve and have any bypassed boost pressure go back to the inlet side of the turbo. Read the following for more information:

"The factory recirculation valve(s)/compressor bypass valve(s) on cars with MAF sensors work very well at keeping from having the compressor surge issue (boost pressure trying slow the turbo compressor down very rapidly) common on factory turbocharged vehicles without these which is their general purpose. Also with the air flow from the compressor outlet being put onto the compressor wheel keeps the momentum of the compressor/turbine wheel moving so you get quicker turbo spool response as you accelerate through the gears. The compressor bypass valves were designed to open at a certain amount of engine vacuum and when they open, they move the bypassed air flow (recirculated) into a hose then back into the inlet side of the turbo so that none of the calibrated air that was measured from the MAF sensor is lost out of the system. If any calibrated air flow is lost from the system, the ECU will not compensate for this and this will end up with a rich condition between shifts and stalling when stopping quickly while getting out of boost. There isn't any easy way to easily go around these issues when using aftermarket BOVs on a MAF sensor based control system which is why we do not recommend using aftermarket BOVs. Cars such as the 300ZX-TT do not gain any hp by changing the OEM recirculation valves, just a louder noise when they open and the rich/stalling issues explained above."

In regards to mechanical oil pressure gauges, yes, you should run a braided hose or solid metal type line to avoid the high possibility of a plastic line failing which would lose your oil and oil pressure and potentially cause engine failure along with the mess from oil leaking in the engine bay or worse the interior of the car. As a minimum, a bulk head fitting could be used on the firewall so that the engine bay side can have the braided oil line and the interior side of the oil pressure line to the gauge could be a hard line like a copper tube. This way with the engine movement, there would not be any hard line fracturing and no plastic line to fail. You could still use a hard line from the engine oil pressure signal but somewhere before that goes to the firewall, there should be a flexible braided hose since the engine does have significant movement.

They both agreed on my oil pressure line issue. It's just hard to go one way or the other cause both these shops are some of the best in cali and have been doing what they do for like 60 years combined.

[evildky]

Whats confusing you? They said what I said, atmospheric bov's on a metered air injection system = a rich condition. The only thing I see here thats confusing is the implication that an atmospheric bov can "help with idle and less tendancy to stall". Not sure who said that but I disagree, I see no way possible for a bov to have any effect on idle unless you replace a leaky bov with one that doesn't leak, the iacv would be the itme to look at if you have idle or off throttle stalling.

[CerberuSlol]

Whats confusing you? They said what I said, atmospheric bov's on a metered air injection system = a rich condition. The only thing I see here thats confusing is the implication that an atmospheric bov can "help with idle and less tendancy to stall". Not sure who said that but I disagree, I see no way possible for a bov to have any effect on idle unless you replace a leaky bov with one that doesn't leak, the iacv would be the itme to look at if you have idle or off throttle stalling.

No Mckinney says that happens with recirculating bovs that it has less tendency to stall and help with idle. Although on most of his cars they run atmospheric cause them and the customers sometimes don't want to go through the hassle of setting it up for recirculating. and they can run full vent to atmosphere or run a hybrid 50/50 and jim wolf was like doesn't even chance it. Although I bet for jim wolf since they are tuning a bunch of maf cars as well don't like the hassle of having to tune for vent to atmosphere bovs.

Mckinneys last email stated "There are different ideas of what is best. Jim is technically correct, and everything he says is true, but there is no hard YES or NO…

There is no gain as he says , so it comes down to the difficulty of actually doing the recirc. Most people like to hear the valve work….

AS for the mechanical gauges he is correct stay away from the nylon lines and insure there is slack for engine movement"

I think since I already have it welded for a vent to atmosphere greddy bov Im going to get a new greddy and once I tune it hopefully this month can sort s*** out so I'm not running so rich between shifts.

[evildky]

You can not tune a meterd air car to not run rich between shifts with an atmosphereic bov.It'sa contradiction and anyone who says it can be done does not know what they are talking about, a lot of Z32 guys regurgitate this misinformation. The tuning is based on the amount of air being measured and if you are letting an unmeasured amount of air excape fomr a metered air system there is no way to correct for it period. Mckinney is a swap shop, they made their name making swap parts and pieces for those lacking the skills or energy to fab their own parts. Jim wolf made his name making nissan/datsuns making speed parts for Nissan/Datsun engines. Completely different businesses. I call BS on the statement that a bov will have any effect on idle, this would only be possible if there were a leaking bov or mating surface. Nissan metered air aystems that came factory turbo'd with factory recirc valves require very little in order to use an aftermarket recirc type bov verses an atmospheric bov as they are already set up to recieve the return air. Most ricers do love to hear the whoosh of the bov going to atmosphere. Early Nissan/ Datusn turbo cars wiht metered air EFI systems did nto come with any bov or recirc valve at all, in these cases it's more work to add a recirc valve than to add an atmosphereic valve but you can either do the job right or take a shortcut. I'm not a fan of cutting corners.

[CerberuSlol]

I think what he meant is with a new ecu and like an safc and translator they can adjust it. Also After talking to jim wolf mckinney go fast bits and some other people since at idle while the bov is closed atleast the piston inside looks closed. and you can hear a whistle as if it's open a leak in the bov it's self whether it's the seal or a bad diaphragm could be causing my boost issues. My car should be stalling out if it's 0 vacuum at idle so I do believe that's wrong and my gauge is messed up as well a boost leak. I took off the hose to the boost gauge and put my finger to plug the hole and I could feel suction so I do have vacuum there but the gauge just might be a bit screwy especially since I have a boost/vacuum leak in the bov it's self I'll find out tomorrow when I replace the bov and see how the gauge response and how the car responds. I'll either be switching to a go fast bits respons bov to do maybe like a 50/50 recirc/vta setup or go with a greddy type rz and get a recirculating fitting.

[CerberuSlol]

You can not tune a meterd air car to not run rich between shifts with an atmosphereic bov.It'sa contradiction and anyone who says it can be done does not know what they are talking about, a lot of Z32 guys regurgitate this misinformation. The tuning is based on the amount of air being measured and if you are letting an unmeasured amount of air excape fomr a metered air system there is no way to correct for it period. Mckinney is a swap shop, they made their name making swap parts and pieces for those lacking the skills or energy to fab their own parts. Jim wolf made his name making nissan/datsuns making speed parts for Nissan/Datsun engines. Completely different businesses. I call BS on the statement that a bov will have any effect on idle, this would only be possible if there were a leaking bov or mating surface. Nissan metered air aystems that came factory turbo'd with factory recirc valves require very little in order to use an aftermarket recirc type bov verses an atmospheric bov as they are already set up to recieve the return air. Most ricers do love to hear the whoosh of the bov going to atmosphere. Early Nissan/ Datusn turbo cars wiht metered air EFI systems did nto come with any bov or recirc valve at all, in these cases it's more work to add a recirc valve than to add an atmosphereic valve but you can either do the job right or take a shortcut. I'm not a fan of cutting corners.

Have you seen the pics of my car. your probably right even though mine is a 1987 I believe it is setup to recieve the return air.

[CerberuSlol]

[youtube]http://www.youtube.com/watch?v=L7k2-hpetzU[/youtube]
[youtube]http://www.youtube.com/watch?v=9e7pdUBgS68[/youtube]

Heres a shaky video of some of the issues with the boost gauge if you link me points in the video that you have questions about I can tell you what we were boosting and what the vacuum was at. [youtube]http://www.youtube.com/watch?v=1NeRwpMKUAM[/youtube]

[evildky]

When all the intercooler piping has been replaced with aftermarket it's hard to argue that it too difficult to pipe in a recirc type bov. It's a lot less work to pipe in a recirc valve than to do the engine swap, or to convert to a vertical radiator. Your profils says 450whp, so what injectors, ecu and turbo are you running? The stock parts won't get to this level. I'm no fan of advertising estimated HP, either you know or you don't. Stock injectors turbo and ecy you'd be lucky to see 300 whp.

...and your steering wheel is on the wrong side.

[CerberuSlol]

When all the intercooler piping has been replaced with aftermarket it's hard to argue that it too difficult to pipe in a recirc type bov. It's a lot less work to pipe in a recirc valve than to do the engine swap, or to convert to a vertical radiator. Your profils says 450whp, so what injectors, ecu and turbo are you running? The stock parts won't get to this level. I'm no fan of advertising estimated HP, either you know or you don't. Stock injectors turbo and ecy you'd be lucky to see 300 whp.

...and your steering wheel is on the wrong side.

yea it's not necessarily accurate at the time when I put that in my profile we were putting in a gt30r turbo and getting it tuned from jim wolf with the 94 maxima ecu but s*** didn't work out that was the horsepower we were told we should get just forgot to take it down sorry. After the swap I was around around 300hp even with my big 60 pound rims. The steering wheel isn't exactly on the wrong side since the car was an import from japan. It came with an rb20 my mechanic of Plumb Performance swapped in the rb25 for me.