I've done it so many times.. All you needed to do was search under my name, and you will get posts all the way from year 2000 and the info I've shared on my Integra builds + my other cars over the years, and videos to go along with it showing the difference.

My turbo Camry, from 10.5:1 to 9.5:1. And then down to 7.5:1 CR. Difference? I lost about 40 WTQ from 2000-4000RPM going from 9.5:1 down to 7.5:1. Boost came in like before, but the initial 3-4 PSI of boost was there just to make up the compression difference. So my engine needed about 3-4 PSI of boost just to make the same as 0 PSI of boost at 9.5:1 CR. My car no longer chirped the tires off the line because the turbo had to spool first before it wanted to go anywhere (brake boosting became mandatory), and I had a 3.0L V6 motor with 7.5:1 CR. That's why it has a supercharger + turbo now.

My turbo IS300 with stock internals (10.5:1 CR), and then swapped over to 2JZ-GTE internals and a TT headgasket. Compression dropped to 8.2:1 CR. It's no longer a peppy 3.0L inline-6 it used to be. It now feels like a Supra down low, and eats gas like one...lol But the pistons came from the Supra, so you can't beat free handed down parts from another car in the garage.

My Integra, went from 11.5:1 CR, down to 10.5:1, and then down to 7.8:1 CR (current setup). Difference? Instead of having 130 lbft of torque from 1500-4000RPM that I used to have, I now have 105 lbft of torque instead. Real life difference? That's like driving a D16 single cam, versus a B18C5 Type-R. So the real life comparison in terms of response and power delivery is really, just like comparing a D16 vs a B18C5 with or without boost. D16 makes about 100-105 lbft of torque until about 3000RPM, and needs about 5-6 PSI to match an ITR; and a B18C5 makes about 130 lbft without any boost.

The ONLY reason I drop compression is due to power vs octane. I wanted those big numbers on limited octane. But on a small GT28RS? Must be smoking crack to run 7.1:1 CR on a 320 WHP turbo setup in a B16.

You can run 7.1:1 on your motor, and obviously it will "run", and it will make boost. Doesn't mean it makes good sense or becomes a good practice by killing efficiency unnecessarily.

 

One of the most fun street cars I have ever driven was a 10:1 4 door GSR with the disco potato and a 9500rpm redline. The powerband was almost instant and wasnt too much power to just blow the tires away, it would spin 1st and 2nd some though. So a 10:1 B16 with that turbo would be a blast to drive, put a LSD in the trans and rock out. 93 octane shouldn't be a problem for that compression.

 

Tony the tiger has been around a long time, he knows his ****.. See unlike you, Tony has actually done testing and had real world experience and gives you the information he's gathered..

I notice a lot, that you go around trying to call people out and TRYto prove them otherwise..

 

Good real-world experience based tech in this thread.

 

Im not doubting any ones imput on here but does any one wonder if there is any other sort of problems relating to the low dyno numbers that this setup put out other then cr?

op should post a dyno sheet so we can see exactly whats going on. just saying it could be a combo of things, maybe a small boost leak?

 

As apposed to what? just agreeing with what the og's say? I haven't called anyone out i simply stated why i feel he shouldn't tear his entire engine apart so he can have a slightly more efficient set up. And i asked the op questions pertaining to why his numbers were low that he HASN'T answered.


So where's the problem chief?

 

I am all in for the tech as always... Never had beef with anyone actually, so to get back on topic, the issue with compression doesn't always lose power in a fixed percentage. I know the general rule is about 4% per 1.0 compression difference for stock engines, but turbo motors are no different than N/A engines and require decent compression to function properly. Once you fall off the "grid", the losses can be well beyond 4% per point of CR dropped.

An SR20DET for example, or like most factory turbo engines have ports, cams, intake and so forth meant for low compression. Low compression means air is moving very slowly because the engine can't "suck and push" as much as a high compression engine. A really low compression engine would hate big cams, and also hate high RPM's to sum it up quickly. That's why stock turbo motors like an SR20, or an RB26, or a 2JZ are so sluggish out of boost and off the line. On a Honda with boost, lag is minimal in comparison because they breathe and make power without the boost, and we all can run big power on relatively high static CR. Any surplus in boost (ie: 1 or 2 PSI of initial boost) is always more torque and power on a Honda.

Our B-series Hondas really hate low compression. On a D16, or perhaps even an H22A, motors with lower redlines, less cam, less overlap and generally motors that have a bottom-end coupled with a lower flowing cylinder head do not get affected as much by a huge drop of compression as much as another high revving high breathing engine like a B-series, K or F series in comparison.

It's no different than dropping the compression greatly on a Honda S2000 F20C or F22C. We have witnessed a lot of these motors making extremely big power with smaller turbos and being highly efficient with high compression ratio (10.5+). Depending on how the engine makes power from the factory (which an F20C for example, does it through high VE and very well breathing setup in N/A form), will lose a lot of power not even just in N/A form, but also in boosted form if the compression was drop by several points. Instead of having 30 WHP per PSI of boost, it will end up being like 20 WHP per PSI of boost with really low compression. The engine loses more power as more boost is being ran.

Boost is also a main determining factor in terms of engine efficiency. It's pressure acting against the intake valves, and also the exhaust valves (intake vs exhaust pressure ratio). Once you run boost into the high teens (18+ PSI), you will notice that power begins to decrease in terms of HP / PSI of boost.

So the basic thinking of "running more boost" to make up for the loss power in compression doesn't necessarily hold true anymore. If the B16A now loses power due to lower CR, and now it also needs to run an extra 4-5 PSI to make up for the loss theoretically; then in reality, it probably needs another 7-8 PSI on top (in total) just to make the same power due to the losses from running higher boost. All of a sudden, instead of getting 240-250 WHP at 10 PSI of boost which is the norm, it now needs at least 18 PSI peak to get to the usual norm with 7.1:1 CR. At higher boost, efficiency falls off further due to air being more compressed, turbine is working harder (higher exhaust pressures), etc.

I am pretty sure the low numbers on the OP's setup is strictly due to the compression ratio.

 

Hello again and thanks for the input....we are not sure if its 7:1 from the pistons or what. I bought the motor already built for cheap (now i know why). All i know is it has cp pistons and eagle rods. It has a ported head with the complete buddyclub spec 4 valvetrain, cams, and camgears. (seems like that head is for all motor.... would it affect my numbers?) it has an itr im with a haltech plat 1000 ecu. also a b18c vtir jdm tranny/ excedy clutch. I have 2 boost settings on my controller... 8 and 20psi. If i run the car on 8psi it feels slower than a stock type r. (i have a dc5 r and a dc2 fully built turbo r). I can say for certain it is about 7:1 but we cannot say what cr they are....(cp never made a 7:1 so i am confused since the original owner said it was cp)

 

What are the specs of the BC cams? That could be your next problem. You may have way too much cam for a smaller GT28RS turbo. Did your tuner adjust the cam gears? I can't remember on top of my head if CP offered custom pistons for B-series, but I know most other companies offer them. Do a quick engine compression test and see what the numbers are. It will help you determine a rough measurement of compression ratio.

 

As a former user of the Buddy Club 4 cams on even an NA application, there was just too much overlap to dial out even to be efficient in the 5000-10,000 rpm range of the torqueband. Using a small turbocharger like the Potato and a big cam like a BC4 is really not going to be fun for the tuner. Find out your true static compression, bump it back up to about 10.0:1, then go back to GS-R cams (or even B16). This actually would be the easiest thing to do.

 

i have a b18cr cam would this suffice?

 

As in an ITR camshaft? yes.

 

7:1 mad low hope u plan on pushin 40psi on the street lol


go 9:1 or 5