how bad will boost spike with downpipe?
 

I have a few questions. I was wondering if I installed a downpipe, would I need to also install a boost guage and a boost controller to make sure I won't get boost spike? Will I even get that much spike to where I need to worry about it? Also I have a Apexi EL boost guage and tempature gauge but I don't really want to put them on my car because I might be selling it pretty soon. Also which downpipe is the best or are they all good? There is an HKS downpipe for $199.99 on the RX7 club store.

Re: how bad will boost spike with downpipe?
 

I think it would always be a good idea to install a boost gauge just so u always know what your turbos are boosting anyway but I don't think you will need a boost controller. I have an HKS downpipe and A'PEXi EL boost gauge on my car and I don't really get any boost spiking. I get something like a 10.5-7.5-9.5 boost pattern with the HKS downpipe as my only mod.

I would get a SS DP instead of a mild steel one. Unless you don't plan on keeping the car for that long. You can usually get a used SS DP for $150-200.

I have a friend with an otherwise stock car except for M2 intake and M2 downpipe and he has no spike. The car is just really smooth now. I never did this sequence or had a ride with this setup till recently ... it was nice. My car had all three, intake, dp, & cb and I got a spike. The powerFC will cure that though. Just another thought as you mod your car.

You should have the boost guage in before the downpipe.

I have the M2 intake, Pettit SS DP, and Blitz cat-back. I've never gotton spike with this setup. Before I put in my boost controller I had a perfect 12-10-12 boost pattern with absolutly no spike.

you should probably get the SS DP just to prevent any rust or corrosion, or you can get the HKS DP and get it coated with that jet hot stuff. It'll probably end up around the same price if you do that. I've heard the HKS DP fits better because of the way its made. I think the other DPs are just a 3" pipe thats bent to fit in the right spot but the HKS is made some other way. I'm not sure about this though.

You will not get any boost spike with just a downpipe but just like everyone else said get a boost gauge as soon as possible. The only mod I know will get you boost spike is a mid pipe. You will be fine for now.

I had some spiking when i first got my downpipe. Like 13-14/8/10. Right now I have Pettit intake,ss down and catback. I did some adjusting with different "pill" sizes to help control the primary spikage. "Pills" are holley jets that can be interchanged in the boost orfice. I am currently running jet size 67 in there now. I fooled around from 64 to 69 and 67 worked best for me. This is a cheap alternative to control this problem until i save for a stand alone, midpipe and intercooler!!