I installed hard intake pipes over the weekend. Went for a drive and floored the car. My boost went past 12 psi and I immediately let off. Prior to the hard pipe install the boost pattern was a perfect 10-8-10. Would the hard pipes cause that much of an increase in my boost level?

Thanks,
CWTG

93 Touring
Stock ECU
Stock IC
Racing Beat Catback
Rotary Extreme Cold Air Intake
Jet Coated M2 DP
Stage 1 rebuild from RotorSports Racing ~4,000 miles

 

The hard intake pipes shouldn't make that much of a difference in boost (actually, they shouldn't make any noticeable difference), but that's not to say it's not possible. Are you sure there aren't other variables in the picture that could be the cause of the "over 12psi" reading you're seeing?

 

you probably had a small leak which the pipes resolved. They should not increase boost substantially.

 

Some people say that the old rubber intake pipes compress under hard acceleration while the motor is sucking a lot of air into the engine.

 

It's not uncommon to get boost spikes after modifying your intake. You might also see it more now if you are having some cooler weather as well.

 

I appreciate the information. There were no other mods done at this time. It is the first time in a couple of months I have floored it. I am a rather conservative driver, want the car to last many more years. I have the car in a storage building most of the time now, no garage. I will adjust my boost controller down and see what happens this weekend.

My next mod will be a PFC and Commander. I will take it easy until then.

Again thanks for the information.
CWTG

 

Really a leak before the turbos will cause a boost increase?

 

I noticed that when I took the large bottom hose off it was misshaped, pushed in at one point, which I think would limit the amount of air passing through it. I am quite ignorant of the workings of the car and am not an engineer (medical laboratory education and experience). I do not want to screw up and blow an engine especially since it is slightly over a year since done. Once I saw the boost go that high I just took my foot off the accelerator, listening for the ping of detonation. Did not hear that, thank goodness. I expected boost spike to remedy itself in less than a second but did not time anything, just got off or it.

The weather was somewhat cooler this past weekend but not cold by any means.

CWTG

 

A couple years ago I did a test of the stock system. On a stock car the turbo outlet psi is 13psi (3psi higher than what actually gets to the manifold). Your hard pipes are allowing less turbulance compared to the ribbed stock pipes therefore less boost pressure is loss. That's why you have the increase in manifold psi.


You should also notice slightly better throttle response!

 

At stock boost levels with the stock turbos, any turbulence in the intake pipes caused by the ribbing is basically inconsequential to the actual ability of the turbos to breathe, because there are so many bends already in the piping. You will see much more of an effect by changing the flow capabilities of the airbox/filter than you will the piping (this is other than an old weathered and weakened stock piping that collapses under boost, which is a different story)

I installed hard intake pipes running 13 psi with full intake/exhaust bolt-ons, and saw no difference whatsoever.

 

Do you know what your turbo outlet PSI is? You have more mods than we do. You already have a full intake and exhaust to go along with the tuning at 13psi. Correctly tuned there is no reason for you to get any additional spikes with your set-up. I have a modified stock box but I don't see anywhere near 12psi on the primary like he does. Even in cold weather I didn't get that kind of spike on the primary.

I still feel the increase comes form the loss in turbulence (due to the lack of the turbulent ribs in the piping) and increased air flow to the manifold. I'm not sure why you feel the hard pipes shouldn't be making that much difference? Less turbulence = less pressure loss which increases flow.

 

Knowing what the "turbo outlet psi" is in this case only matters if you are able to view actual changes in boost pressure by swapping from the stock hoses to hard pipes via a gauge of some sort.
I used to get spikes up to 13 psi with the stock ribbed piping with modified stock airbox/DP/stock cat/CB consistently if I wasn't careful. The hard pipes didn't change that at all.
The difference is that the piping that actually matters with regards to airflow is fairly smooth: the stock metal piping that connects to the turbos. Once the airflow approaches the turbo impeller area, it speeds up, and that's where smooth airflow really matters. It's like the velocity stacks on carbs or the old mechanical fuel injection units; there can be all sorts of obstructions, etc. to upset the airflow heading to those velocity stacks in an airbox, but it doesn't really matter. Unless the airflow is seriously turbulent before it gets to that hard piping by the turbos (which it isn't, otherwise you'd see major gains by just installing hard pipes), it doesn't really matter all that much.
If the stock intake piping was one long straight pipe to the turbo impeller area, then I'd think about turbulence possibly making a difference. Unfortunately, there are multiple bends that the airflow has to take to both primary and secondary turbo piping, which slows it down considerably. Thus, it doesn't really matter until you get right up to the impeller entrance.

 

Why does your sig say you have dp/mp/cb if you had no other mods done at the time? With most of the restriction take out of the flow into/out of your engine it is understandable that you would get creep.

 

^Same here. And regarding t-von's suggestion that it's due to mods, I'm still fairly stock. The only difference that I noticed was that I could hear the whine of the turbos spooling more with the hard pipes.

 

Sorry for the confusion, I meant no other mods at that point in time. The intake and downpipe were done prior to the engine rebuild. When I had the engine rebuilt I had the catback added and then tuned for 10-8-10. I don't have a mid pipe. I really appreciate all of the information. My knowledge of the turbo system is very limited; ie high boost will kill an engine with stock ECU. I don't want to detonate and have to get another rebuild.
CWTG

 

What intake piping did you buy?

 

Gramps,
I bought the hard pipes from RX7 Store. Had to cut 4x with hacksaw to get a fit on the lower pipe. I am also a gramps. Repreciate the question; never too old to rock and roll.
CWTG