I have a 1999 Series 8 RS which is a 280ps model with 99 spec turbos. The car is basically stock except for the Apexi twin intakes and a Fujitsubo cat-back exhaust. The car still has the stock catalytic converter and ECU. I installed a Defi boost gauge the other day to allow me to see how the car is boosting and give me more confidence running to redline. Unfortunately, I discovered massive boost spiking when the 2nd turbo comes on at 4.5k RPM so I only did three 3rd gear pulls and didn't keep my foot in it when I saw the spiking occurring. Effectively, what I'm seeing and hearing is:
- Primary turbo boost: c.0.75-0.8 Bar (maybe slightly over)
- Secondary turbo boost from 4.5k RPM: Spike to just under 1.0 Bar and then bleeds off to fluctuate between 0.8-0.9 Bar (could be slightly lower or higher but hard to know for sure when concentrating on the road)
- Loud air fighter jet-like whistling noise when the second turbo comes on. Never noticed it before the gauge install. Sounds really cool but makes me nervous.
Factory boost on this model should be about 0.75 Bar and with the Apexi filters and Fujitsubo cat-back I expected maybe up to 0.8 Bar at most. However, the boost I'm seeing is too high and doesn't make any sense to me. I didn't experience any fuel cut and the car pulled like a train the entire time I had my foot in it (which was very brief) so I'm not sure where to start with the diagnosis.
Oddly enough, the previous owner whom imported the car from Japan drove it like he stole it and never had any issues and I haven't had any issues yet either. I also had the car compression tested recently and it was F: 7.7, 7.6, 7.6 and R: 8.0, 8.0, 8.0 so the motors at least pretty good for now.
I intend to use this car on the track and was hoping to do one track day before the weather gets sour but I have to fix this first.
Can anyone offer any advice?
Where are you plumbing boost gauge from?
The middle nipple on the UIM that was capped.
Hi mate...cant blimin remember but i know i had mine hooked up on the uim some where and it was really sensitive there was a guide on the internet rx7club that went through an install. If memory serves me correct i t,d into line that fed vac line feeding boost sensor. Prob worth waiting for somebody else with better knowledge. That jet noise is concerning though though sounds like a boost leak poss silicone joiner....would play havoc trying to build consistent boost and give you the readings your getting.
That's fine taking a feed from there and the boost pattern looks ok as well
Sounds like the whooshing sound is coincidental more that anything else
Wouldn't a boost leak mean I would be getting less boost rather than a spike? I've tried to search the various forums for twin turbo boost issues but more than 95% of the topics are about low boost on the 2nd turbo or no boost at all. In this case I have boost from both turbos at the right times but the issue is when the 2nd turbo comes on the boost spikes to between 0.9 and 1.0 Bar which can't be good. Why would it spike like that? Is there too much pressure being scavenged off from the primary turbo and thus overspooling the secondary when it is supposed to come on? Is the wastegate then overwhelmed which is why the boost only ever settles to between 0.8 - 0.9 Bar?
If I get a chance I will try to take a video of the issue. I just need to find out how to mount my phone camera in the car to get a look at the boost gauge. In the meantime, any advice to diagnose the problem would be helpful.
You said you have a Defi boost gauge, with controller? Then you can record the boost pattern via the controller and playback on your gauge and record on your phone when stationary.
I'm not sure the Racer Gauge series records anything as it doesn't use the Advance Control Unit
You would need the digital gauges and controller - how about a passenger doing the video?
I think I've got it. I have a very wrong suction mount which I can attach to the driver's door window and angle it at all of the gauges. I will try it out when it's not raining which might be a few days.
Your getting boost creep due to a free flowing exhaust and aftermarket intakes. The standard ecu cannot control the waste gate quick enough to regulate secondary boost. All you need is a restrictor plate fitted into your exhaust.
When you do have a look through your cat, my guess is all the honeycomb has blown out rendering it nothing more than a decat
Well, the car "passed" MOT in January just fine and I am pretty sure the cat is still working as the RX-7 smells nothing at all like the RX-8 I had before which only ran a resonated mid pipe. It smells much more like a normal car would to be honest.
I recognize that the boost levels are slightly higher than standard due to the intakes and cat-back exhaust, and the spikes very well could be due to the intakes flowing too well compared to stock. I'm in the process of locating a stock airbox (preferably a late spec one) to put on the car and see if it helps the problem.
One thing I've learned from all of my searching as well is that I should check the oil injectors since they tend to clog up on the S8 cars and fail a lot more frequently than the earlier cars. It could potentially explain why there is oil on the front of the turbo on the rubber hoses? Although I'm still inclined to think the turbo oil seals are on their way out if they are actually original turbos with c.81k miles on them. Still, I need to get around to taking the UIM off and replacing all of the vacuum hoses and checking the injectors anyway.
Just had a thought. Would I be better off installing my Apexi Power FC and running it on the base map? I've read that the base map is extremely rich and could be a better solution than the stock ECU until I can get it tuned.
If the oil injectors or omp fails you will likely lose the motor mate , they have no effect on boost levels whatsoever. I would just get your apexi mapped and end of trouble. Just because your ecu is an S8 it's still not capable of dealing with mods either put it all back to standard or get your apexi mapped to your car