okay so here's my question, my car had it's engine rebuilt 30K miles ago by rotary performance in texas. for whatever reason, they refuse to give me full details into the engine rebuild but did mention that it was rebuilt using 3 mm seals and had some level of porting done on it. i currently idle at 10" VAC, which from what i've read, is the result of HEAVY porting. rotary performance did mention to me that the total cost of the rebuild was nearly $8,000 when they did it. so aside from that, can i safely boost past 10 psi? it already spikes to 12-13 at WOT when i drive, but of course i let off as soon as i see it happening due to fear that it will detonate. it seems like the engine is pretty robust, but what els would i need to do to safely boost past 10? thanks in advance

 

The determination of boost levels has more to do with fuel support and charge temps rather than apex seal size and porting.

 

if the engine was ported, it should have been tuned right afterward...

please tell me your not still running on the stock ecu?? what mods do you have?

 

rotary performance has not told me if it was tuned immediately afterwards. they're being very uncooperative with giving me information about the rebuild for some reason. my mods are:

downpipe
pro 1 exhaust (does not seem to be extremely free flowing, pretty quiet)
apexi intakes
upgraded aluminum radiator
upgraded aluminum AST
aftermarket clutch and flywheel

that's about it. oh and the engine rebuild, with the 3mm seals and porting. i have not checked the ecu yet, but as far as i know it is still stock.

 

So you paid $8,000 for a rebuild and they won'teven tell you what they did?

I've never heard anything but positive feedback from RP but from what you say they sound like shady scammers. I've never personally delt with them, but this sounds out of character

 

I'd physically go check the ECU. If you're running on the stock ECU, 12-13 psi is dangerously high, especially if no fuel mods have been performed. If the ECU is stock, you need to find a way to get your pressures under control.

 

Reading between the lines here, it sounds like you got the car AFTER this rebuild was done. It IS a bit odd the RP is not being more forthcoming with information, but then again in this day and age of lawsuits, I can imagine them going into a non-committal mode when someone starts asking questions about a rebuild they did months or years ago.
10" of mercury at idle is pretty low, I have a pretty aggressive street port and I still pull 16 - 18 inches at idle.
I am also struck a bit by your assertion that your exhaust "does not seem to be extremely free flowing, pretty quiet". An exhaust does not HAVE to be irritatingly loud to be decent flowing. When you look at your overall mods, you basically have an intake and exhaust as performance enhancements as well as this undefined port job. A $8K engine SHOULD have some goodies in it, but not necessarily. One could assume that it is a $4K engine and the shop charged $4K for labor, you know?
Regardless, on a stock ECU you are playing with fire to go overboosting, period.
With no fuel upgrades such as injector work (even a good cleaning and flow-matching is important) or a higher volume fuel pump, you CAN have some problems.
Your saving grace is you still have a stock I/C, so you are not necessarily living on the edge with each drive, you just have to be careful.
Some sort of boost control is definitely recommended. You just shouldn't go bumping 12 - 13 psi.

 

thanks, i'll look into the ECU issue. i know that my boost spiking is a problem that i need to deal with asap. do you recommend any particular boost controller?

as far as the engine rebuild, it was $8,000 and performed by the previous-previous owner. rotary performance has given me general details about it, but when i asked for more information, they said they could not tell me about the rebuild due to "customer privacy issues". whatever that means...i know they are a reputable shop and do good work (my engine runs strong and returned excellent compression numbers). i just don't get why they're so hesitant to tell me exactly WHAT they did.

 

sounds like he just bought it, and the seller is the one being shady. 8k for a rebuild is unheard of from my standpoint.

how long have you owned the car?

 

It was not tuned if you are still on the stock ECU.

 

yes, thank you, it was purchased after the rebuild was done. i try my best to keep boost at 10 maximum, which for the most part, it DOES. however, i have found the boost needle rise to 12-13 on occasion at WOT, which of course, i let off as soon as i notice.

oh and the fuel injectors were replaced with two 550 and 850 cc injectors a month ago (i'm assuming stock though since those are the same sizes as stock)

now i'm curious, if you're pulling in 16-18 at VAC idle, what does my 10 VAC idle mean?

 

I wouldn't say that unless we know what all the work detailed. I would bet that RP did all the R&R work which is a majority of that 8k. It was probably a turn-key job.

 

I will let more experienced/savvy rotary gurus answer the seeming low vacuum question. There could be several things, or combination of things. You might just have a REALLY huge port job, but it would likely 'lope' a lot at idle...sounding like a large-cammed piston engine. You might just have a vacuum gauge that is not accurate. I defer to others on this one.

Guys?

 

I'm probably out of line here, but I'm saying it. Bajaman hit most of what I was going to write. But from a shop stand point; your calling because you don't now what's done to a car. So, you don't know the car very well and you bought it not knowing what exactly you were getting. The shop my have had the car in for work on XX/XX/XX date. But, once the car left there is no way for a shop to know what the owner did to the car. So if they tell you what they worked on, and you still think it's done to the car, then the motor pops(sounds like you are heading that way already), you would end up on here bashing them for your popped motor. For instance; lets say they tuned a PFC and told you that. You, not knowing what one looks like, thinks it still in the car. And you run the car like it has a tune. Only to find out the guy you bought it from took the PFC out before selling it to you and put the stock ECU back in. $8000 on a build has to includes parts too, or maybe all new everything, like hoses and things that are for reliability. There's no way a light port rebuild is going to run that much alone. Unless Chuck Norris built the motor to be indestructible, like he is.
My suggestion would be taking it to a shop, RP is already familiar with the car. Let someone who knows what they are looking at walk you through the cars set up. Finding the right core group of people who KNOW rotarys is the first mod someone should get. My .02. Good luck

 

well it's true that i purchased it without fully knowing the details of the motor itself, but i ran a compression test that turned out very good numbers prior to purchasing and figured that was a good indication of a healthy motor to start off. the test was part of a diagnostic test that i had completed at MazCare in atlanta before purchasing, and they said the engine was in great shape. i can understand RP being wary of backing their engine since it has been some time since they worked on it, and i would never bash them for a blown engine that has changed owners twice since they last saw it. i just wanted to get more details to the rebuild from them so i knew exactly what kind of rebuild it went through. i don't think my motor is going out anytime soon, but i do believe the boost spike is due to a lack of a boost controller (which can be fixed easily).

The $8K price they quoted me may have included labor, i'm not positive. my boost gauge could also be inaccurate, but it seems to read the 10 psi at WOT fairly well too. the porting job COULD be a huge one and that's why it stays at 10 VAC, but the idle is smooth and quiet (not 'loping' like someone had said earlier). i should take a video of my starting my engine perhaps to give you guys a better indication. the engine runs perfect and idles like a baby. in fact, i wasn't even worried about it until you guys telling me now that 10 VAC is highly unusual.

anyways, i will end up taking it to a shop to look at but i thought that maybe i'd try asking on the forums first to see if anyone had some ideas first. thanks again for your input

 

boost gauge is a possibility. mine reads good from start, to the transition, to redline..but the vac is way off. i also have great compression. my gauge decides not to work sometimes also.

do you or a friend have an extra boost gauge? that way you can test both?

 

Good luck man. And don't go boosting past 11 psi!

 

your gauge sounds similar to mine then. why would the vac be way off if the boost measurement seems dead on? also, since we're on the topic of boost gauges, i have noticed that in 2nd and 3rd gear at WOT, the needle will sometimes hover around 5 and not go past, even though the car FEELS like it's pulling hard. when in 4th and 5th gear, the needle jumps to 10 easily and stays there (spiking to 11-12 if i really keep pushing down on the throttle). is it possible to have inaccurate boost readings on certain gears while having accurate readings on others?

 

I had a bad boost gauge once also. Get another one.

And get a boost controller before you blow the motor. Or temporarily replace the 2 lines with the pills until you have time to get one. Doing so will limit the car to 7 PSI.

 

i will, manual boost controllers seem to be the economical way to do this. is it necessary to get a full blown electronic boost controller?

 

Why don't you call the prior owner, and have him give Rotary Performance permission to release information to you .................... DUH!!!

 

the car has changed owners twice since RP has seen it, the previous owner hasn't been able to get in touch with the previous-previous owner. i've already tried this route...

 

It doesn't matter. What boost you can run depends on your fuel and charge temps as I mentioned above. Whether your engine is ported, has 2 or 3mm, etc doesn't matter all that much. The first thing to investigate is your ECU. One you have an ECU to support higher boost levels, then you need to make sure your charge (intake) temps are cool enough to support the boost levels you want to run.

You didn't list an aftermarket IC with your list, so if you are running the stock IC you'll definitely want to get an aftermarket unit when increasing the boost.

 

I bought a second boost gauge just for the purpose of testing mine every now and then. If you were close you would be more than welcome to borrow mine, or I could send this one to you perhaps, we could work out some shipping deal. It is a large gauge, like 3" diameter and you have to run the vacuum line out of the bay and into the car thru a window, but it works great for this purpose....

 

I repeat what the others said, get a boost controller and check for vacuum leaks.