Quote Originally Posted by Main Stream View Post
What is the plan for the car? This will help in determining what is needed. Is it for drag racing, highway pulls, fun weekend car, mountain runner, etc. What power numbers do you want and is it usable power. I would take a 275whp d series on the street over a 400whp d series.

Here are my suggestions, in my opinion.

I would go with 9.5:1 or higher compression. With only a 1.5L and if you run a big turbo you need all the help you can to spool the turbo and have usable power. Whats the point of 400whp if it is only for 1k rpm. You can do this compression or higher just fine on pump gas.

Pick a turbo for your plans. If you want 300whp then pick a turbo that can make 350whp. Don't have a 600whp turbo on a motor that can only make 400whp. Also, 60 trim is just the cut of the wheel. You can have a t28 60 trim or a BW s372 with a 60 trim. Two totally different turbos.

Airflow is critical in making big power with small motors. This is for both intake (intercooler piping, etc) and exhaust. Make sure everything is well made and smooth flowing. A good 2.5in downpipe will be enough is made right (made 565whp on 2.5in downpipe on pump gas).

Don't shim oil pump. Honda pumps make enough pressure. Even with a very small shim you will see well over 100psi at redline. Just causes more leaks. Unless you plan on running very very loose bearing clearances just run a stock pump.

Good luck with build and keep us updated.

First, it's a Honda motor. They are designed to make peak power at the top end as I'm sure we can all agree on. When somebody says 400whp on a vtec motor, it's pretty obvious it's going to make 400whp at the top of it's rpm limit since power climbs steadily, granted that generally speaking, single cams (depending on the cam) will tend to level off sooner than a DOHC Vtec motor. Same thing generally applies to lower boost levels as well.............. Basically, if you want to be in the 300 whp range, from 4-5k up, you shoot for higher peak numbers. Nothing new here other that this can be worked around is some cases through the use of an electronic boost controller and boost by gear by rpm. Basically, you increase boost at the lower rpms to bring power up to your target goal, then reduce boost appropriately to maintain power level all the way to redline. Click the following link for a perfect example of this technique being used properly:
http://www.importatlanta.com/forums/...-Gas-Dyno-Tune
Assuming that the valvetrain is there, which in the case of the OP it is, this means that your comment regarding the 1k analogy holds no ground.


The following link will take you to a D16Z6 making nearly 400whp on high boost and nearly 275 whp on low boost.
http://www.importatlanta.com/forums/...-E85-Dyno-Tune
For the record, the bisi cams that the OP referenced will actually spool this turbo quicker and make more power (30-40whp) than the comp cams referenced in this link. This is only as a reference since it's a similar build. The boost by rpm function was held steadily throughout the rev range in this case instead of increasing boost at the lower end and reducing at the top end like the previous setup.

In regards to the 60 trim, don't take it out of context. The mid 50 to 60 trim range, preferably closer to 60 in order to take advantage of the Bisi cam is what makes sense. There is always play room as to what trim turbo can be used for the application. However, to even suggest a S372 is beyond illogical. They don't even make it with a 60 trim wheel. I hate to think you are being over dramatic for whatever reason and would like to think of it a simple mistake.

Sizing a turbo is not just about power but about the operating rpm range and that's usually dictated by the cam, which is usually dictated by the application. A GT30R, GT35R, or Precision 60-1 with the corresponding a/r ratio would be ideal in the OP's case.

You fail to take into account the Bisimoto 2.4 cam. Excellent turbo cam by the way. With a turbo of the specs previously mentioned, I wouldn't be surprised at all if carried 400whp past 7k and into 9K territory. Well above the 1k rpm range you mentioned.

There is no question to high numbers can be made with a smaller exhaust. I think we can all agree on that. However, the smaller the piping, the more boost has to be given to compensate for the restriction. In other words, a 3" exhaust puts less stress on the motor than a 2.5" since less boost is required to make the same power. I shouldn't have to say that, you are just as aware of this as I am.

In regards to the compression and oil pump advice, good general comments.