Catless midpipe increased boost pressure.

[codex]

So, I recently replaced my broken WG with an ATP WG and that ran at about 9 psi. This MSP also has a FMIC. Today I installed a catless midpipe. The car sounds different now, but not really an exhaust sound, more like a turbo sound. I noticed that the car is now boosting to about 10.5 psi. Is this too much to run? Is it normal after installing a catless midpipe to get an increase in boost?

 

[Wagonbacker9]

thats a little high without a tune, but it is normal for both the FMIC and opening up the exhaust to up the boost. helps everything flow better. It shouldn't "technically" work like that, but there are a lot of physics principles at work I don't care to understand, so "better flow" is where I let the rest go and assume people with degrees could explain it. LOL

 

[codex]

So, a catless midpipe with an ATP wg runs at over 10psi? Everyone I heard that has one only has 9psi, like me before the midpipe. Its not knocking or fuel cut or anything like that, but it was about 35 degrees outside today, with 93 octane.

 

[codex]

Does a setup like mine come close to 200whp? I'm guessing at least 180whp.

 

[Wagonbacker9]

honestly, 200 could be easy with a good tune.. with my FMIC I put down about 160 (iphone dyno, so grain of salt on that number there) with no other power mods.

With my SSAFC if I upped the boost I'm confident 200 would be about the number I'd hit.

 

[Jeff_C]

Is it normal after installing a catless midpipe to get an increase in boost?

Yes. By removing the catalytic convertor (which is almost ALWAYS the biggest restriction in an OEM exhaust) you have increased the pressure differential across the turbine. Greater Δp without adjusting the wastegate will generally lead to a higher peak boost pressure.

 

[codex]

So am I safe at 10-11 psi with a stock ecu? It feels like it is running great, and I would think the rich ecu tune would be ok for the increased psi.

 

[Wagonbacker9]

i wouldn't say safe.. plenty of ppl have blown up cars at that boost pressure.

 

[Jeff_C]

Forgive my ignorance on the subject, but what is the weak point in your guy's motors? Are the rods snapping off at the small end?

 

[Wagonbacker9]

rods in general... the FSDE engine is the same regardless of factory turbo. if you search "zoom zoom boom" you can find several pictures of holes in FSDE blocks

also worth noting, the oiling system isn't great either.

 

[yudkib]

10-11 without a tune is pushing it a little... much like wagonbacker, i wouldnt say youre safe there. do you have a wideband? if i recall correctly, theres a rough spot in the fuel map at like 5600-6000 rpm, it goes from being like a 9.8:1 mixture (super rich) to like 12.7:1. on larger boost its just game over.

 

[codex]

Well the only reason I thought that 10.5 psi would be safe is because I've read quite a few posts here that say that 200whp is safe on our motor and transmission. Are we saying that 10.5 is over that HP number or just that the factory tune is unsafe at this boost level?

Also I have no way to lower the boost, I replaced the WG from suggestions of people on the forum with the ATP and everyone said it was fine running at the increased pressure that it offers. Do I really need to buy another lower PSI wastegate to not blow up my motor?

ps: whats the least expensive 'tune' I can get for this motor?

 

[Wagonbacker9]

SSAFC running the superstockmap. 400 bucks new, maybe 300 used.

200 is safe tuned... but untuned, realistically nothing is safe. LOL

I sound like a cynic, but people have blown stock engines.

 

[yudkib]

the tune is unsafe, running more boost makes it unsafe-r. substantially. the stock tune can support maybe 170-180 at the wheels, but the stock block and bottom end is good to about 250whp. 275 if youre good.

also, i thought the ATP WGA came at 6psi, midpipe and exhaust work etc shouldnt put that past 9psi. you should call ATP or whatever vendor you bought it from, you might be able to get it replaced as a defect.

 

[Wagonbacker9]

check if its leaking, also check your vac source, make it as short as possible from the IM. but the ATP is supposed to be a lil over stock level, and opening it up does explain being higher than that. I wouldn't assume defect.

 

[yudkib]

yeah a little over, not 5.5 lb. i understand the less restrictive argument, but thats quite a bit to gain from exhaust and IC

 

[Wagonbacker9]

like I said, physics understanding beyond mine is required to speak with authority. and its really more like 3 psi.

6 stock, plus one or 2 for the WGA, plus the rest for opening it up.

 

[codex]

Since I'm most certainly going to blow this motor. Can we use any FS-DE in the MSP from any Mazda that comes with the FS-DE and has either an automatic or manual transmission?

 

[yudkib]

10.5psi isnt a guaranteed motor blow-up. but if it does blow, anything 00+ is a direct swap, for sure... i think like '97 and older 626 need sensor swaps. im not sure about in between.

 

[codex]

I found an '00 626 FS-DE with 45k miles its from an automatic though and is only $500, right by my house.
Any different parts that I would need could be swapped from a blown MSP engine?