how much boost is too much?
 

So I have an fd that is all stock except for a downpipe from what I can see, and my blitz dual turbo timer (really old school one I think) shoots up to 0.78 kg/cm2 (aka 11psi). From what I read, the car should be kept at a strict 10psi without any supporting mods to the fuel system. Is this extra psi dangerous?

11psi isnt too dangerous but try to keep it at 10psi to be safe. Just adjust it with the controller. Look for a used reflashed ECU (pettit, m2)on the forum and set your boost at 11-12psi. It should be a solid and safe setup.


Also, if you ever do up the boost make sure you get a new Intercooler as the next mod.

I did plan to do a few more basic mods though. I thought that the powerfc was the way to go on these cars?

Will the pettit ecu be able to adapt to mods being done one at a time?

If I am reading correctly, it allows one to open up the breathing and then turn up the boost. I thought that this was a forbidden act on FDs!

The power fc is the most widely used, understood, and supported programmable ecu.

The pettit unlimited ecu is a non-programmable ecu that is reliable to support the gamut of BPU combinations. It is also well regarded but not recommended for custom turbo applications or modified fuel set ups.

If you plan to keep your car as is, you do not need to do anything more. 11 psi is perfectly safe with only a downpipe. Enjoy it, and drive it worry free.

This thread brings a tear to my eye. It's like the good old days, with lots of informative answers that are spot on. Bravo, gents :icon_tup:

:D

I am really liking this forum. I used to frequent a 240sx forum, and those people were just too smart for me apparently.

Only reason why I mentioned m2 and Pettit ecu's is to avoid the cost and hassle of getting a PFC and tune for such a simply modified rx7. It will be better, of course but the the performance/drive-ability gains of PFC will prob marginal in comparison to the price difference. So if you have big plans for your FD in the future, I say PFC. If not, either type of ECU is perfectly fine.

I really think a Rx-7 with a downpipe, catback, SMIC, ECU (whichever, set at 12psi or less) = a fun and reliable FD.

and thnx Rich :icon_tup:
nothing is more valuable on forums then ppl giving their opinions based on experiences we've learned from. (sometimes the hard way) :)

Iirc stock injectors max out at 14psi?? Its just that you need a good ecu to support it which is why people are mentioning m2 or pettit because its an affordable upgrade.

If you're on the stock ecu, like me, then I don't think 11psi will hurt.

Whoa that Pettit ecu looks like only around $200-250...probably the way I'll go for now. Does it matter whether you pick one up that is meant for California or not? We only have 91 octane here. And does it pass smog? Or do you need to switch it out with stock for the test?

petit ecu
 

the Petit ecu is fine for CA, even with only 91 oct. passing smog is fine also, but probably will need the factory oem cat(s) installed and really hot before testing.

The Petit ecu is really just a stock ecu, with a bumped up fuel map to give some headroom on the boost side of things up to about 13-14 psi but then fuel system (injectors & fuel pump) is maxxed out. If you search you might find some posted information about the fuel mapping which is "supposed" to be good up to 14psi.

I have been waiting to install my parts but basically, I have a stock car (15k on rebuild) with BNR stage 3's, Bonez DP, stock main cat, RB catback.

My upgrades for this summer include:

- Petit ecu (already have)
- Bonez high flow cat (already have)
- cheap bastard stock air box mod (search for this.. good stuff) with K&N filter
- Supra TT fuel pump. (need to get one)

- HKS evc S boost controller w/simplified sequential setup ( http://www.hksusa.com/products/more.asp?id=3723 )

- Greddy smic (bought used) & pipe kit ( http://www.rx7.com/store/rx7/fdintercooler.html - http://banzai-racing.com/store/rx-7_...er_piping.html )

- aluminum intake piping ( http://www.turbohoses.com/rx7.htm - http://www.rx7store.net/product_p/polishedpipekit.htm )

Planning to stay within 10-12 psi for boost which is plenty for fun in the sun all day long :) and gas prices above $4 YEAH :eek:

^prepare yourself for over $5 :(

The gas companies are going to make record profits!

I have previously argued that 10psi is not a hard-and-fast number for a stock ECU and a mostly stock engine (let's say downpipe only). I say this based on material Mazda has published about the 13B-REW and the sequential turbo system in general. For example, according to the REW SAE paper this is a boost curve they achieved on the REW as compared to their control (a single turbo engine used in testing):

https://www.rx7club.com/attachment.p...1&d=1292428133

80 kPA is about 12psi.

There is different boost control logic based on ambient conditions, gear position, closed loop feedback, etc. If you look at the "over-boost fuel cut zone" outlined in the service manual, marked by the top line, you will see that higher boost levels are acceptable between about 3000 and 5500 rpm.

https://www.rx7club.com/attachment.p...1&d=1292428518

I'm in the planning phase for my stock FD as well, since it's somewhat related, if I had a downpipe and aftermarket catback, would I be able to add a Greddy elbow and aluminum intake piping to the mix, or would I want an ECU first?

Also MrNizzles, where do you plan on mounting the EVC-S? Is that something you would tape or mount over the steering column or would you mount it elsewhere?

Thanks

Greddy intake will do little to the tune. It is essentially just the same pipe just in a different material.

Due to the nature of the FD it is always best to have an aftermarket ecu before modification. Worst case: bought an ecu. Best case: saved your engine.

Seriously, you can get a pettit or m2 for cheap.