Ask anyone, 177.0 horsepower to the wheels from 1.6-liter normally aspirated engine is pretty impressive. What's even more impressive is when you consider the B16A engine still has an untouched cylinder head and stock bottom end. We know Honda engines are durable but the B16A is downright awesome. Our B16A is 15 years old, going by the production stamp on the head, and still sings to 9,500 rpm without any problems. The best part of B16A engine is that it is fairly affordable; most engine depots sell them for about $500. Add a few bolt-ons like we have and you get one heck of a powerplant.
For Part Three, we finally opened up the B16A engine for a ported and polished cylinder head from Port Flow. Unfortunately, to meet the deadline we were not able to have one ported specifically for the 1.6-liter B16A engine so we had to borrow a ported cylinder head from Dynamic Autosports. The head they loaned us was off their B-series shootout engine they did for our sister magazine Import Tuner. Not only was the head a GS-R unit but also ported to match the 2.0-liter engine for the shootout. We weren't expecting the mismatched cylinder head to do much on our 1.6-liter engine but decided to test it out anyway. The GS-R head features a squared semi-circular combustion chamber versus a cicular combustion chamber of the B16A (43cc GS-R vs. 45cc B16A). So we were going to be running a slightly higher compression ratio than before.
Also we had to swap out the intake manifold with a Peak Performance intake manifold made for the GS-R head. Removing the B16A head is a straightforward R&R job. Once removed we inspected the cylinder walls and were astonished to see the walls still had the factory crosshatching on them. Pretty impressive since we guess the engine has about 80,000 miles under its belt.
Not wanting to take a risk with the old head bolts we swapped in a set of ARP head studs for a GS-R. When swapping a GS-R head onto a B16A or B18A/B make sure you use the GS-R head bolts since they are longer than the B16A and B18A/B. The shorter head bolts can cause the threads in the block to stretch and pull through, possibly destroying the block threads. With the new head gasket in place the GS-R head was mated to the B16A bottom end. Our GS-R/B16A hybrid was buttoned up and it was back to the dyno the following day.
Our guess was that the cylinder head was going to perform better at the top-end but lose power lower in the rpm band due to the larger ports. The dyno proved our theory correct with the hybrid engine generating 180.17 horsepower an increase of 2.57 horsepower over the stock B16A head but lost horsepower below 7,000 rpm. Our guess is the port work was too big for our smaller displacement engine. It just proves that swapping out a cylinder head specifically ported for one engine does not work on a different displacement engine. Since our B16A engine will be displacing 1.9 liters once we are done we are positive the ported GS-R head will work much better with that combination.
With the Integra still strapped to the dyno we tested out the N1 pulley from Honda. The N1 pulley eliminates the power steering and air conditioning portion of the pulley making the pulley much lighter. Since the Integra wasn't running power steering and air conditioning adding the pulley seemed logical. On the scale the N1 pulley was 3.0 lbs lighter than the B16A unit, measuring in at 1.5 lbs. On the dyno the pulley made marginal gains from 6,000 rpm to redline with gains of one to two horsepower. The pulley did push the peak output of the engine to 181.30 horsepower.
Our last installment for the day was testing out a ZEX wet setup nitrous system on the Acura just for kicks. The owner had the kit laying around and we were curious how the engine would react to the nitrous. We decided to be safe and retarded the timing a couple of degrees and close the gap on the plugs a bit to prevent detonation.
The Integra liked the juice peaking out at 221.09 horsepower and 160.30 lb-ft of torque, an increase of 39.79 peak horsepower and 46.94 lb-ft of torque. At 7,800 rpm we witnessed a jump of 50-plus horsepower over the non-nitrous run. Like we always say, when you are down on horsepower there is always nitrous.
Making horsepower is always a tough proposition especially when you push the engine closer and closer to the edge. In normally aspirated trim we were only able to increase output by 3.04 horsepower over the previous installment but with nitrous we gained 43.83 horsepower more than the last installment.
We feel there aren't many more bolt-ons we can add to pump any more power out of the B16 so we are going to DEFCON 5; the bottom end is going to be opened up for more displacement. Next time we will be back with a full 1.9 liters and we will spin the rollers hard in an effort to break the 200-horsepower barrier in N/A trim!