I have the Defi II (discontinued) BF boost and oil pressure gauges in my mostly stock 05 Evo VIII and the controller (or one of the gauges) is freaking out and causing it to all misbehave so I am due to replace. I was hoping to get some feedback on 3 things.

1. I have never felt I can trust the boost gauge as it seems to report higher than expected values for boost than what I understand stock is. It seems to shoot past 22 PSI a lot. In researching, I see that many people have attached vacuum tubing for boost to a different location than I. Any input as to whether or not this mounting location is unwise or resulting in less than accurate readings? See the bottom attached picture. The top yellow circled is the current and I marked the common place I see people installing instead.

2. Before I plan to do any modifications such as a MBC or EBC and slight boost increase, I feel an accurate measurement of boost is a requirement. I plan on keeping my car forever and just plan to do some moderate mods in the near future. I don't want to risk doing too much and risking longevity and I have nobody I can take it to in order to tune so it will need to be Etune. What are some good options for trustworthy/accurate boost gauges still around for my car? I saw some posts about the AEM brand ones might be good. My A pillar dual gauge pod is for 60mm though so I might have to change that if I don't find good 60mm options.

3. With plans to do some moderate modifications eventually, TBE, MBC/EBC and Etune (since I have no shop around where I live)...is a wideband AFR for a second gauge really needed or suggested? I currently have oil pressure as my second. I don't have the ability/skill to mess with my own tuning so if I am sending the data off for an Etune, is a wideband even needed? I would like to have it "set and forget" and be a daily driver still. I bought the car new (now at 89k miles) and I am ready to put a little more weeeee factor into it..



Top is current, bottom is where others tap into boost. Does it matter or should I move mine?

 

Question 1) that is the same spot im tapped into fpr boost so id say you're good there.

Question 2) when my evo was stock, i had a boost gauge installed and was frequently seeing as high as 25 psi which i knew was not good as i was not tuned. It would even hit fuel cut. What i did was install a manual boost controller to limit the max boost and that worked well until i was able to get a tune. I have had an autometer boost gauge that has been trouble free for about 10 years. Id say any major name brand would be good.

Question 3) the AFR gauge is not needed but highly recommended simply because it can let you know if something is off. I only installed mine when i got tuned for e85. Its an AEM sensor and has been working great.

 

I thought most people tap into a vacuum port on the intake manifold for the boost gauge.
The 3 most common gauges people run are AFR/Boost and Oil pressure.
If you do e-tune you will have to run an AFR gauge and type the wire so that you can log afr for the tuner.

 

Best option for <30psi of boost is the JDM/Evo 10 MAP sensor. It just bolts in place of the stock unit and provides data that is easy to log for E-tuning etc. It also allows the tuner to do direct boost control with the tune vs. load based boost control. If your >30PSI you probably need to do an SD conversion anyway and a 4-bar map sensor is required and usually is also a bolt on replacement for the factory MAP sensor.

Yes you need a wideband that can be logged for tuning. Aside from that though any modified car should have a wideband to watch out for issues.

The gotcha about T-ing into the factory regulator line is that you want to do it between then manifold and the solenoid and not between the solenoid and the regulator. The solenoid can block pressure signal to the regulator so you need to plumb in before the solenoid to get a constant signal.

 

The modifications I am looking into are going to be on the lighter side. I only want to get some more HP without pushing it too hard or having to change a lot. Rumor has it that I can use a MBC and increase the PSI a couple pounds, add a 3" TBE and have someone etune and I can get a fair amount out of my engine without risking anything. The only engine mods I have done so far is removed the stock air box and have the STM filter with stock MAF and no etune yet. I just want to make sure I am setting myself up for success and not risking longevity.

If I read correctly, the stock MAP only reads 1 bar so I can buy a JDM MAP sensor but I would need to modify my ROM right...eeek. I have ECUflash/Evoscan but haven't started using it. If I do this, the Evoscan can start reading/recording boost where it couldn't before and that would be the main reason to do this, right? It makes the etune process safer/easier but it doesn't really change anything else about the car.
https://www.evolutionm.net/forums/ec...tructions.html

There isn't already a place to put an AFR sensor on the stock exhaust is there? I have a bit of chicken before the egg situation. I wouldn't mind getting a new boost and AFR setup before moding but don't want to drill/weld into the factory exhaust so I may have to change exhaust before I will have a place to connect the AFR to. Will changing to 3" TBE without a tune cause any issues since it will change my back pressure? I assume our cars have an after CAT exhaust sensor but I haven't even looked to see if there are any sensors past the turbo. I haven't yet started researching what TBE exhaust I would want so I am still at the noob stage on that part.

 

The ROM does need to be rescaled for the jdm map sensor or it will throw a check engine light. The values are well documented though and its really just a cut and paste job into ecuflash. Logging is one benefit, but another is boost control. The stock system is calculated load based and with the map sensor upgrade you can have it be psi based. The benefit of keeping the stock boost control and using a 3-port bcs is you get gear dependent boost control, boost cut on knock, different boost profiles for different maps, and over/under boost correction. The only tune you could get without AFR's would be like an off the shelf tune that the tuner has made with specific parts in mind. Even then every car is different, and you really want to be able to verify what AFR's are doing. You could add a bung into the factory downpipe for the wideband gauge, or upgrade the downpipe. You should probably upgrade the 02 Housing while you are at it.The Megan racing housing is the best bang for the buck out there and outperforms pretty much everything else. There are 2 narrow band oxygen sensors in the stock setup, the "front" 02 which controls closed loop / fuel trims, and the rear 02 which only monitors catalyst effeciency. Most people delete the rear 02 sensor and instead wire the wideband analogue output into the ecu through the rear 02 channel for logging and safety monitoring features of Tephramod V7.

 

I ran my turbo-back exhaust without a tuneand thats when i had my overboost issue. Your car will run but not the same as all stock. So running mods with no tune would be entirely up to you.

My humble opinion would be at this point to get a hold of a tuner you trust, (local or e-tune) and ask them what they need on the car to get it tuned. Tuners use different tools for tuning based on their skill/preferences. And since you plan to stay with mild mods, I would not expect you to need more than a wide band and a boost controller (some tuners prefer MBC, others electric control, some will do either).

Without spreading misinformation about stock o2 sensor compared to aftermarket, my tuner told me he prefers the new AEM wideband because it responds quicker to changes in A/F ratio. Again thats just what my tuner told me and i trust him.

I would also like to add that it is very important to have all the maintenance up to date, (im sure you know but just wanted to say that anyway).

Also, a fresh oil change and a new set of spark plugs wouldnt hurt either.
*MOST IMPORTANT* Make sure you have done a boost leak test and have no leaks. Boost leaks will mess with the tune and you will not be at optimal performance regardless of mods.

 

Thanks for the details. I will be building a boost leak tester and do that this weekend.

On the wideband AFR, I see lots of references to installations that only use the voltage and ground. Unless something is tying back into the ECU somehow, an AFR gauge would only be for my piece of mind. The Ecuflash/Evoscan would have no way to gain access to what info the new gauge is providing so my tuner (not being there to see it) would have no way to gain access to what it is showing. Or is the new X-Series OBDII Wideband AFR Controller Gauge a way to address this and it will be plug and play so that the tuner gets the extra AFR data?
https://www.aemelectronics.com/produ...and-uego-OBDII

 

There is a seperate serial connector to be able to log the A/F. It will plug into the back of the sensor display pod along with your power and ground wires and o2 sensor connection. The serial conmector is about 30 dollars or so.
https://stmtuned.com/collections/mit...-logging-cable

 

For tuning you will want to use the serial connection for speed. Evoscan can pull in data from a bunch of different widebands, but you might want to keep evoscan compatibility in mind when choosing a sensor. As I was saying before you can wire in the analog 0-5 volt output of the wideband into the ecu rear 02 sensor input. This will allow you to log the sensor directly through evoscan (no serial, but slower) and enable some safety features in tephramod. Those would be MIL/CEL flash on AFR out of range and boost cut on AFR out of range. You can set the flash frequency/duration differently, so you can tell low knock, high knock, and AFR Out of range apart easily.