Im looking at buyin an 88 rx7 and the guy says that the engine is rebuilt with a "mild" streetport. My question is what is normal idle rpm for a "mild streetport" because he says that it idles at 1500 and that it is normal for the setup but it seems really high to me.

 

rough idle can be a issue that isnt just caused by streetport, they may not know what they have its most likely air in his radiator

 

1500 RPM indicates a stuck cold start thermowax. A mild streetport will have a stock idle of 750 RPM. There could also be a large vacuum leak.

 

thats what i was thinking. he also says that he had rteck remove the aws and warm up systems. Y i dont know.

 

"aws" is the warm up system. Accelerated Warmup System. Removal is a standard feature of the Rtek and you do want this. Your idle problem is most likely related to the thermowax or vacuum leak as Aaron has stated. Beyond that it could be related to misadjusted cruise control linkage, idle adjust screw setting, or improperly set TPS (throttle position sensor). The Rtek is not the problem.

 

Depending on what he removed when the "warmup" system was removed, he may have simply left the cold start cam in the "cold" position when he hacked up the car.

 

I'm interested in this too, my car has a fairly rough idle with a very aggressive street port (previous owner was building the car as a track car before I bought it).

How would air in the cooling system affect idle out of curiosity?

 

off topic kinda but whats the difference between mild street port and Larger street port...pros and cons of the large street port vs. mild.

 

It really shouldn't. The coolent temperature affects the thermowax. The thermowax is designed to bump idle up to aroun 1500 when the car is cold. as the temp of the coolent rises the thermowax lets the idle lower down until a point where it no longer is effecting idle. If you are really having problems with excess air in the cooling system it may be technically possible to effect the temperature that the thermowax is seeing but this is highly unlikely in reality.

Once warm the idle of an aggressive streetport could be rough. This is just like changing the cams on a piston engine. If you go to extreem, think nascar engine idles, it will idle like crap, if at all, at stock idle speeds.

 

It is just a sliding scale of increase in high end power power and decrease in mpg, low end power, idle smoothness. It is a trade off that has to be considered with how the car will be used.

Real world I am seeing 16 mpg highway on my large street port. If I was stock port I would be seeing 25+ highway with all my mods consistent.

 

ok i see, so then a bridgeport would see like way less than 16mpg for sure right?

 

It defintily would

 

Mixed use I see 14 or so. Bridge could easily put you below 10 mpg depending one how you drive. City you could see 5-7 and highway maybe 12? Considering what a bridge port does that may be worth it. Crazy power in the upper RPM range for what it is. Be prepared for a 1500 rpm idle as well.