xb2002

Can stock twins keep up with a ported motor? A mild street port. Non seq they will boost to 14 and fall off to a consistant 12 in 4th and 5th gear pulls around 6000 rpm. avcr , fmic, powerFC, 850/850, fp, dp, mp, cb, pulleys, etc...

Anyone else ever have this problem? Does it sound like the twins are just going out? We found a cracked bov, replaced and set the avcr to 1.2 and it boosted to 18, but still dropped, so we turned it back down to live. Also what craps out on the twins?

1QWIK7

iTrader: (33)

xb2002

I tried searching and I could find any solutions to my problem. Just one other person in Malaysia that had the similar problem

spekdah

you know, if everything was avaliable in SEARCH then no-one would post questions, wheres the fun in that?

scotty305

iTrader: (2)

I believe the stock turbo's are running at or near their peak efficiency level from the factory. This is to keep lag to a minimum, which was the reason to go with the sequential setup in the first place. Upping the boost will produce way too much heat vs. the amount of additional flow that you're creating.

It sounds like you need a big single turbo for the amount of power you're looking for.

-s-

1QWIK7

iTrader: (33)

well i didnt mean to sound like a dick.. what normally craps out on the twins? well you were trying to boost 18? so yeah, boosting beyond the turbos limits would be one reason..

i agree with the guy above me..

xb2002

werent trying to boost to 18 on purpose just went too high with the avcr...

Yes I know a Big Single is in the future just wanna run theese till then.

patfat

I can hold 15 psi on my car. I'm using a ProfecB. I have my car set at 14 psi though.

areXseven

iTrader: (1)

Our Hitachi HT-12s were built to withstand a little above 22 psi. Our stock IC and fuel management system was not.

jimlab

Says who?

oakridgerx7

where are you getting your info from?

saburo

iTrader: (1)

22psi seems alot for the small pissant turbos stock on the RX-7

EpitrochoidMan

^^^ no doubt

I wish I had new turbos :-(

scotty305

iTrader: (2)

I searched for almost an hour and couldn't find compressor maps for our HT12 turbos; I tried HT-12, tried google, tried rx7club.com, but no luck. So we're left guessing why your turbo's seem to be running out of steam. My guess is that they're built to do that. Here's why:

Imagine you're a mazda engineer, and you want your new car to have great throttle response. You want this so much that you opt for two turbochargers and a whole bunch of other crap to control them. It would be more than obvious to run the turbos near their peak efficiency levels to minimize spool-up time. If you're not familiar with these terms, this link might be helpful to you: http://stealth316.com/misc/3s-turboguide.pdf

Stock engine management will cut fuel and timing at 13-14psi, correct? There could be a few reasons for that, such as the fuel system and intercooler not being able to cope with that much extra air, but I'd bet that's about the point where the turbo's are starting to run out of steam, where they start to increase the heat and reduce flow. Another thing to consider, the reading displayed on your boost gauge is the pressure at the intake manifold, it might not be the actual pressure being developed by the turbochargers. I believe the intercooler and piping cause a pressure drop, though I don't pretend to know exactly what it is.

How are your IAT's, EGT's? , A/F ratios?

-s-

xb2002

We just had the car tuned last friday by Steve Kan. Iat is around 40c( i think) in town and lower on the highway. As far as the egt and a/f ratio.... not sure. I can watch the stock o2 in the comander and it reaches .89 v which is close to 900f
I think. We are running plenty of fuel(black smoke when boosting) I guess its just time to go single.

O yea... Searching sucks on this issue... I looked everywhere also...

areXseven

iTrader: (1)

I believe the data is contained in the RX-7 book written by Yamaguchi. I'll locate and post the data from the actual page a little later.

widebody2

you do realize that there is no way thats possible, right? The stockers will crap out after 15 minutes at 22lbs.

jimlab

Actually, the motor would be gone long before that, even with race gas. 22 lbs. is so far out of their efficiency range that it's absolutely ridiculous, not to mention the fact that they're not large enough to sustain 18+ psi to redline.

areXseven

iTrader: (1)

I found the data which is located on page 113. My office computer does not have the neccessary software to compress scanned photos/documents. I'll have to post the subject data/page from the house tonight.

But the data is written as follows:

Maximum boost,in.(mm)Hg: 22.4 (570)

xb2002

Will they sustain 14? Because it boosts to 14 and sustains to 12.

matty

i heard of a few people that run 18psi....but they general loose boost towards redline.

areXseven

iTrader: (1)

Here's the data "cropped" from Pg. 113......

Trexthe3rd

You really should read that more carefully. 22 inHG is not PSI. The conversion factor is 2.03 which would make 22inHG = 10.837 PSI

jimlab

areXseven

iTrader: (1)

Oooops.