Thanks: 0
Likes: 1
hey to all the subby mechanics got a question. im building a ej25 n/a im puttin a high performance engine kit in.thinkin about borin out to 101mm and raisein compression to 10.5-1.but im not concrete on the borin never done it and im curious if i will see any hp gains or more importantly torque gains.my other question is about portin my intake manilfold and heads and port and polishin exhaust ports on head. gonna post on forum later today too.
Really no need to go that large of a bore, the biggest increase you will notice will be through the compression increase. Far as the the porting and polishing goes it is def. a big help to your engine doing this. for the intake side you want to port this out as nicely as possible to ensure the air isnt being restricted but you dont want this to be perfectly smooth because you want atomization. However for the exhaust side you want that to get out as quickly as possible so port this and polish it smooth to keep better flow. Rule of thumb with porting an intake and intake side of the head that anything before the injectors can be smooth anything after have texture for atomization...exhaust side smooth to allow the escape of hot exhaust gases.
il send you a link to a all motor ej25 build
i was gonna do the same spec setup, i tried calling them for some help got no answer, but i never seen videos on it an ontop idk if its daily driven friendly.
I want to turbo my 99rs2.5 NA on 8 pounds of boost stock will the motor hold that at all ?
Originally Posted by subbyfiend
Zach makes some great points. I agree with everything he has said. I'm going to go a little more in depth.
As for your questions...
- Boring = no (there's no reason, and it will take more airflow and cam to get power out of it in the upper RPM's where it will start to take away from the lower end and it's going to end up costing too much)
- Higher than 11.5:1 compression = no (without engine management)
- Boost - BLEH. No... I'll explain in a moment.
---
I'm assuming that you're starting off with the stock Phase 2 EJ251. This is an excellent starting platform for an NA build, but I wouldn't suggest putting any boost through it. You'd spend a little bit more on an NA build that will be more reliable, make more power overall (as well as way more torque down low), and have something not too many people have.
---
Now, on to my suggestions:
- Increase compression
- Increase Intake/Exhaust efficiency
- Add more cam
These three simple aspects are what you need to focus on in order to make NA power. How much you want to spend and how much power you want to make will ultimately decided what routes you take for each.
To make it easy, I'll make a few suggestions that should get you near or over 150 WHP without too much trouble (say, in the long term, should you choose to do so) can support at least 240 WHP exactly as I will describe.
- 2005+ 2.5RS Intake Manifold (no port work unless it's to match ports to cylinder head ports. It is already very superior to any other IM you can use and works very well with worked Phase 2 SOHC heads)
- 65mm bored Throttle Body
- Increase Compression (11.0 - 11.2)
- "Equal Length" / "Tuned Length" headers with LARGE PRIMARIES (If you want UEL headers for the rumble, you'll sacrifice a little bit of bottom end power and a little bit of power overall. Personally, the "gained performance" is not worth sounding like a Honda...
- Cat-less 2.5" mid-pipe (if you can get away with having no cats)
- "high flow" "race" muffler
The cylinder heads and cams are where this gets tricky.. Where and how do you spend the money? You also can't chose what kind of cam you want without know what your cylinder heads can do.
I'll make a few suggestions based off of my experience with cylinder heads and cams.
Here's what I know:
- Stock SOHC heads flow very very well.
- Peak Intake flow (CFM) occurs between 0.320" up until 0.450" lift
- Peak Exhaust flow occurs at 0.450" lift (98% of that peak flow occurs from 0.350")
- The exhaust ports are designed to flow less than capable at low lifts to balance lift flow between the intake and exhaust.
- The exhaust should flow in the upper 70% of what the intake flows in order to reduce excess exhaust scavenging preventing "blow by" of the intake air/fuel charge during cam overlap
- The STOCK ECU can only compensate for so much extra air! Build to efficiency rather than max potential if you're not planning on engine management.
- Intake porting can in crease upper and lower lift flow (at the sacrifice of some mid-range lift flow if you're not careful). Upper lift flow can increase by 14% by porting work alone, flowing extremely well from 0.300" and up
- Exhaust porting an easily increase lift flow throughout the lift duration. Gains with porting alone can be up to 5% can be had overall, with 8% increase at as low as 0.280" lift where max ported flow begins and flows up to 0.450"
- 0.350" is the absolute most efficient intake AND exhaust lift to have at the very least with stock OR ported heads without causing too much cam overlap. You're chosen duration will effect the lift, but as long as it end up being at those levels or better you are good to go. And obviously they should be chosen base on Intake to exhaust flow ratio as well.
- A duration of at least 200/200 I/E is a good start (especially on stock ported heads) and will keep the stock ECU happy. No more than 220/215 I/E should be necessary even on ported heads.
BEFORE you do ANY cam or head work, have some new (and modified) valves installed. I would go with a 3-angle all around as well as necks that can somewhat induce "swirl"
- Valves can show 10% increases on cylinder head flow without any other modifications
- BENCH TEST BENCH TEST BENCH TEST: stock, then with valves, then if you do any porting. This will allow you to choose your cam duration.
That's pretty much a large summary of what you should do. I know what I would do, but I can't give away all of my secrets
If you have any more questions, please ask
- Ken
@Zach@TTLM Thanks you sir! #thattookwaytoolongtowriteup !
I can imagine, I was going to quote it but I was like that is way to much to copy and paste. I could not even imagine type it all! lol..
Posting Permissions
Register To Reply
Bookmarks