Is an intercooler 'necessary' ? 2GRFE Supercharged discussion

Hello all,

My big project has been my 92 MR2 with a 2GRFE (3.5l v6) and TVS1320 blower. I made 345whp on e85 w/ Link FuryX

This is honestly plenty quick. However my goal is 400whp, which is the most I am allowed for the spec I built the car to.

Currently it is spinning at 2x engine rpm to a peak of ~14,600 (7300 engine rpm).

I recently did a few tests, normal, no intake element, no eshaust and exhaust cutout closed:

Early AM normal pull: IAT was 133f and hit a peak of 6.7psi.

No intake filter: peak boost dropped to 5.8psi IAT was 145f. 10 degree delta in ambient temps from previous pull

Removed the y-pipe open headers: highest I saw was 4.8psi

Restrictive exhaust: hit 6.5 psi, opened it up again, and didn't crack 6.

Currently I am below the efficiency curve of the blower. I am operating at a pressure ratio of about 1.4. The obvious way to increase this is by installing a smaller blower pulley. I am running e85 and currently am not knock limited. I would expect the relatively small increase in boost pressures shouldn't cause too much additional heat, and I am aiming to spin it to 18k which should put me inline with the blowers peak efficiency. However, my early AM pull shows even a small delta in IATs can have a fairly large impact on overall pressure ratio.

SO what is the general consensus? Is a smaller pulley worthwhile, or should it wait until I am also ready to install an intercooler? I would prefer to not do any additional water/meth injection if I can avoid it.

Regarding the boost variations where the open exhaust had less than the closed, that's down to what boost actually represents - it isn't just a reflection of the air being pumped into the engine manifold, but also of the resistance between the manifold and the cylinder - the true volumetric efficiency. The more inefficient the filling process, the more pressure is required to force the charge through and, conversely, the more efficient the breathing the lower the pressure required to force the air into the cylinder.

In this case removing part of the exhaust will reduce the pressure in the exhaust manifold which will reduce the pressure, and resistance, right through to the intake manifold. I would expect you to have higher torque/power figures with the open exhaust, even if the nominal boost was lower?

I'm very rusty, but it doesn't look like your numbers quite add up - are you sure about the over-drive ratio for the 'charger, and what do you have upstream of the 'charger - if it's on the restrictive side it would explain some things?