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Safe Boost on Stock 13B?
I was interested in learning about what boost levels can a stock S4 13B TII handle safely. This question is assuming that everything is properly tuned and there are not fuel restrictions and such. I would just like to know what the stock internals in this engine can handle safely. Also assuming the engine the engine has a stock port job as well. I assume this question has been answered before, but I would just like a straight answer just to be sure. Thanks
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I would say 14 or 15 psi, depending on your set up.
You don't find very many stock fds now days, even something like aftermarket IC effects your psi somewhat |
^That is a very misleading and general statement. Different turbo's at the same psi will flow very different amounts of air.
The big questions are what turbo? What injectors? and what intercooler? 'Safe' really depends on the individual setup. With bigger injectors, turbo, fuel pump, intercooler, ecu, excellent tune, etc, the block itself can usually handle about 350hp. |
For mines, I try to keep my boost between 5 and 10psi for stock.
I'm playing it really safe. |
Originally Posted by RXSpeed16
(Post 10974523)
^That is a very misleading and general statement. Different turbo's at the same psi will flow very different amounts of air.
The big questions are what turbo? What injectors? and what intercooler? 'Safe' really depends on the individual setup. With bigger injectors, turbo, fuel pump, intercooler, ecu, excellent tune, etc, the block itself can usually handle about 350hp. |
10psi is a good safety number.
On a bone stock engine it's really going to boil down to the condition of the car. Moreover the fuel system. If you have a weak fuel pump, bad fuel filter, or a gummed up injector it will lean out long before 10psi. My personal opinion is that you need a good wideband setup before you start tweaking the boost. It will allow you to monitor the AFR as you increase boost to make sure your not going overboard. Again, personal opinion is the Innovate LC1 system. I'v run several of them and love em for the price. I'm also kinda partial to the TurboXS manual boost controllers. They have made a good combo for me several times. |
Originally Posted by RXSpeed16
(Post 10974523)
^That is a very misleading and general statement. Different turbo's at the same psi will flow very different amounts of air.
The big questions are what turbo? What injectors? and what intercooler? 'Safe' really depends on the individual setup. With bigger injectors, turbo, fuel pump, intercooler, ecu, excellent tune, etc, the block itself can usually handle about 350hp. |
The stock turbo is well outside its efficiency range by about 12 psi. Pushing it further is pointless, and will lead to higher IATs and risk of detonation.
If you're talking about what the engine itself can take, there are few modifications made to the actual block on high-HP builds. IIRC, an S4 rear iron can be broken around the 450-500 whp range. Certain S5 rear irons have reinforced castings, and can handle more. Engines can also be strengthened with additional dowels. |
thank you for clearing that up, what if you have an ECU and then other items that improve performance? is 12 psi a solid number no matter what
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Ive ran 14psi and had no troubles
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Originally Posted by ramo
(Post 10974789)
if you actually read the thread owners question instead of my comment, you wouldve noticed he said a stock car. that means stock turbo, stock injectors, stock intercooler.
Originally Posted by ramo
(Post 10974864)
thank you for clearing that up, what if you have an ECU and then other items that improve performance? is 12 psi a solid number no matter what
Originally Posted by Silver Comet
(Post 10974629)
The block itself and internals (Rotors, apex seals, ect.) Excluding things such as turbo's, intercoolers, fuel, ecu, ect. I don't know how to be any clearer, is it making sense what I'm asking? haha sorry
- Fuel octane rating - Intercooler efficiency - Compressor efficiency - Air pressure (yes, altitude affects this) - Air temperature - Air humidity - Engine temperature (affected by radiator, oil cooler, thermostat, etc.) - Engine load (driving up a hill, rapid acceleration, pulling a lot of weight, etc.) - Compression ratio of the rotors - Fuel/Air ratio - Ignition timing For example, if your engine has 9.7:1 rotors, no intercooler, and a crummy Mexican Ebay turbocharger, and you live in Death Valley, use 87 octane fuel, and attempted to tune the engine yourself, then the engine will detonate at a low boost level. However, if your engine has 8.5:1 rotors, an efficient front-mounted Spearco intercooler, an efficient Garrett GTR turbo, you live in Aspen Colorado, use 115 octane race fuel, and paid for professional tuning, then the engine will be able to run much more boost before it detonates. This is why you need to take it with a grain of salt when forum members chime in about how "My engine runs ten million psi boost with no problem". ;) Given that, see this below website for some good general guidance. It is a bit out of date, so check with this forum before you buy anything that may have been superseded by a better product. For example, the FCD has been made obsolete by the Rtek ECU upgrade. http://fc3spro.com/TECH/FM2W/power.htm |
If you're looking for a good example, my motor's on 70,000KM's and still has 95psi on all faces, and it's been run with 10psi of boost on stock turbo since birth. I just keep my fuel filter fresh, and have an upgraded fuel pump (Walbro 255). I run 94 octane for peace of mind as well.
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Originally Posted by lambof.god
(Post 10976089)
If you're looking for a good example, my motor's on 70,000KM's and still has 95psi on all faces, and it's been run with 10psi of boost on stock turbo since birth. I just keep my fuel filter fresh, and have an upgraded fuel pump (Walbro 255). I run 94 octane for peace of mind as well.
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My setup is:
- S4 13B - S5 Turbo - S6 Rotors - FCD - Blitz Boost Controller @ 10psi - Walbro 255 Fuel Pump - Stock Injectors It's a very basic setup, but it's holding up fine. As for compression, I've had the car 5 months and only checked it last month. I'll probably check it every 6 months. |
Originally Posted by lambof.god
(Post 10978882)
My setup is:
- S4 13B - S5 Turbo - S6 Rotors - FCD - Blitz Boost Controller @ 10psi - Walbro 255 Fuel Pump - Stock Injectors It's a very basic setup, but it's holding up fine. As for compression, I've had the car 5 months and only checked it last month. I'll probably check it every 6 months. |
Originally Posted by lambof.god
(Post 10978882)
My setup is:
- S4 13B - S5 Turbo - S6 Rotors - FCD - Blitz Boost Controller @ 10psi - Walbro 255 Fuel Pump - Stock Injectors It's a very basic setup, but it's holding up fine. As for compression, I've had the car 5 months and only checked it last month. I'll probably check it every 6 months. |
lambof.god, your setup really is the bare minimum to safely run that boost level on the stock turbo. The walbro fuel pump drives up fuel pressure by overwhelming the stock FPR, which is keeping you from detonating in the mid-range. With a stock fuel pump and injectors, there is a lean spot just before the 3800 RPM secondary transition when they hit max D/C under higher boost.
The same setup with a stock fuel pump or even an FD pump would be a recipe for disaster due to lack of fuel and the negative effects FCDs have on fuel and timing calculations. |
whats your estimated hp? The same setup with a stock fuel pump or even an FD pump would be a recipe for disaster due to lack of fuel and the negative effects FCDs have on fuel and timing calculations. To validate my statement about the PO; I recently found out that the fuel filter hadn't been changed for 4 years.. Shocking. |
Originally Posted by RotaryRocket88
(Post 10979190)
lambof.god, your setup really is the bare minimum to safely run that boost level on the stock turbo. The walbro fuel pump drives up fuel pressure by overwhelming the stock FPR, which is keeping you from detonating in the mid-range. With a stock fuel pump and injectors, there is a lean spot just before the 3800 RPM secondary transition when they hit max D/C under higher boost.
The same setup with a stock fuel pump or even an FD pump would be a recipe for disaster due to lack of fuel and the negative effects FCDs have on fuel and timing calculations. |
Originally Posted by RotaryRocket88
(Post 10979190)
lambof.god, your setup really is the bare minimum to safely run that boost level on the stock turbo. The walbro fuel pump drives up fuel pressure by overwhelming the stock FPR, which is keeping you from detonating in the mid-range. With a stock fuel pump and injectors, there is a lean spot just before the 3800 RPM secondary transition when they hit max D/C under higher boost.
The same setup with a stock fuel pump or even an FD pump would be a recipe for disaster due to lack of fuel and the negative effects FCDs have on fuel and timing calculations. |
Originally Posted by RXSpeed16
(Post 10980395)
I've been wanting to swap out my walbro for an FD pump because it was overpowering my stock FPR and running rich on an Rtek 1.7. I know the switchover is lowered to 3500rpm, but has it been verified that the 10psi of boost at stock fuel pressure doesn't have the lean spot?
Here's the thread discussing it: https://www.rx7club.com/rtek-forum-168/secondary-staging-issue-844350/
Originally Posted by fcs4manila
(Post 10980695)
So, does the walbro pump take out the lean spot?
When I measured fuel pressure with my FD pump, it ended up being almost exactly the same as the FSM specs for the TII pump. |
Reviving this to ask a question after doing all my research and searching. What EXACTLY is considered safe on a stock turbo with a high milage engine? Lets say the 160k mi mark. The main thing at this point would be to keep it running as sound as possible. Lets take into this consideration:
-rebuilt hitachi using a 360 thrust bearing and ported wastegate -stock fuel injectors -stock ecu -stock fuel pump -stock everything for the most part |
Thanks for the info RR88! Good stuff!
Originally Posted by REAmemiya_fan
(Post 11015682)
Reviving this to ask a question after doing all my research and searching. What EXACTLY is considered safe on a stock turbo with a high milage engine? Lets say the 160k mi mark. The main thing at this point would be to keep it running as sound as possible. Lets take into this consideration:
-rebuilt hitachi using a 360 thrust bearing and ported wastegate -stock fuel injectors -stock ecu -stock fuel pump -stock everything for the most part |
Originally Posted by Evil Aviator
(Post 10976083)
The OP specified "stock internals", which means stock rotors, eccentric shaft, and associated gears, seals, etc., inside the engine. The turbo, injectors, and intercooler are external.
Excellent question. No, 12 psi is not a solid number. See below for more... A boost gauge is not a very good limit indicator. There are two main factors that limit the amount of boost pressure: 1) The point at which the engine fails mechanically, and 2) The point at which the engine detonates. Since the engine will most likely detonate before it bursts from pressure or strain, let's look at some of the factors that affect the detonation threshold: - Fuel octane rating - Intercooler efficiency - Compressor efficiency - Air pressure (yes, altitude affects this) - Air temperature - Air humidity - Engine temperature (affected by radiator, oil cooler, thermostat, etc.) - Engine load (driving up a hill, rapid acceleration, pulling a lot of weight, etc.) - Compression ratio of the rotors - Fuel/Air ratio - Ignition timing For example, if your engine has 9.7:1 rotors, no intercooler, and a crummy Mexican Ebay turbocharger, and you live in Death Valley, use 87 octane fuel, and attempted to tune the engine yourself, then the engine will detonate at a low boost level. However, if your engine has 8.5:1 rotors, an efficient front-mounted Spearco intercooler, an efficient Garrett GTR turbo, you live in Aspen Colorado, use 115 octane race fuel, and paid for professional tuning, then the engine will be able to run much more boost before it detonates. This is why you need to take it with a grain of salt when forum members chime in about how "My engine runs ten million psi boost with no problem". ;) Given that, see this below website for some good general guidance. It is a bit out of date, so check with this forum before you buy anything that may have been superseded by a better product. For example, the FCD has been made obsolete by the Rtek ECU upgrade. http://fc3spro.com/TECH/FM2W/power.htm Best short answer I've seen for such a complicated question as the OP had in a long time. The learning curve for engine management and function is super steep to a point and then it plateaus and you realize you only need to ask yourself these two basic questions. |
anyone know how to stop the squeak noise on the rear of the 3rd gen rx7
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