This sounds about right. We got very little gains in the rpm range before running out of injector by getting the Afr diled in for E85. Timing wise if we ran either more or less timing than we optimized for gas it made less power. It wanted the same exact timing. The gains were small though under 5 hp/ tq in that range almost in the noise of run to run dyno variation.

Because of the very small difference it looked like was going to make we aborted throwing more money at it tring to source bigger injectors while it was on the dyno swap them out and spend another day tuning.

It has NB 1 fuel system pump, regulator, lines, fuel, rail. But has NB2 injectors.

I'll be going to bigger injectors soon to find out if e98 will make any more power and of course just to have some headroom as 90% dc is just too much.

I also would like to do a CSP engine build after Nats. I told myself I have to be somewhat competitive as the extra power won't do any good if I'm 3 seconds back. Then we'll see how close I can get to Emilio's estimate of 168/140. Or is that from first-hand knowledge?

I presume you mean NA6, since NA8's can make that much on 93e10 :p. When I tired to tune for e85 I hit max duty cycle around 5000rpm's on my 97. AFR's would hangout around 12.8-13, but obviously the fuel was just pooling and it didn't feel right in the upper RPM's WOT. An already not smooth revving motor felt even more trucky.

Thought Id update this. after switching to Deatschwerks 450cc injectors and spending more time fine tuning both for 92-pump and E85 the E85 was good for about a 7 hp gain and with across the range gains everywhere. ~157 hp 143 ft-lbs blue is E85 red is 92pump.

Please allow my to junk up this thread for a second. On a 95 with a VVT swap, could I replicate these results with the addition of a 99+ fuel pump? The motor with have a 99-00 fuel rail and NB2 injectors - at that point is the only missing piece a newer fuel pump, or are my factory lines an issue?

Its an NB2 VVT motor rebuilt with factory overbore and head shaved to minimum spec, with NB1 fuel system lines rail dampers regulator and all. added flex fuel sensor. 450cc injectors. Modified NB1 intake manifold with functioning VICS. few other secret sauce things that are all legal for the class.

Sorry, I guess I wasn't referring so much to the numbers but to the notion that the NB1/2 fuel lines were an integral part of the "E85 on a 'stock' fuel system formula."

Lines are fine, pressure @ injectors is different. USDM NB1/2 is 60psi non-reference. NA is 43.5 referenced. So, NB2 injectors + some way to run 60psi fuel system at WOT = probably G2G.

One of these kits:
https://supermiata.com/Walbro-190LPH-HP-Fuel-Pump.aspx

And an external adjustable fuel pressure regulator (Turbosmart actually makes a really good unit) and you can hit pretty much any power that a reasonable N/A Miata engine is capable of.

We were seeing 92% dc on a stock junkyard un-opened VVT engine on ~E80. That engine was making 132wtq, 155whp. That was with a factory pump, lines and rail from a 95 and regulator and injectors from a NB.