Need New Engine Advice
08-21-21, 11:03 AM
#1
Full Member
Thread Starter
Need New Engine Advice
Hi Forum:
Here is some background. Found a 93 Rx7, had the compression checked, it was good. Bought the car and had it modified with new haltech ecu, wiring harness, vmount, water pump, internal oil seals and pump, tuned to 310hp.
All was good till I started getting blow by through the blowoff valve, then the other day after a drive, the left side of the engine bay was covered in oil, boost was down as well as performance (but car is still pretty fast). The oil heavily smelled like gas. Called the shop that did the work (I moved from the state the work was done in) and after some tests the shop is guessing that the side rotor seals are bad and cant handle the boost causing the blow by. There is no smoke coming out of the exhaust.
So..... Probably time for an engine rebuild or replacement.
From what I have learned so far, a rebuild can cost allot less, but when the engine is disassembled if its found to be heavily damaged, a rebuilt can quickly cost more than replacement.
I am pretty good working on the car, but pulling the engine and replacing with a rebuilt or new engine may be above my pay grade.
So I plan on having a shop do the work. I live in Reno, NV. there is a good shop 2hrs away in Sacramento, Ca.
So looking for some advice rebuild or replace?
Here is some background. Found a 93 Rx7, had the compression checked, it was good. Bought the car and had it modified with new haltech ecu, wiring harness, vmount, water pump, internal oil seals and pump, tuned to 310hp.
All was good till I started getting blow by through the blowoff valve, then the other day after a drive, the left side of the engine bay was covered in oil, boost was down as well as performance (but car is still pretty fast). The oil heavily smelled like gas. Called the shop that did the work (I moved from the state the work was done in) and after some tests the shop is guessing that the side rotor seals are bad and cant handle the boost causing the blow by. There is no smoke coming out of the exhaust.
So..... Probably time for an engine rebuild or replacement.
From what I have learned so far, a rebuild can cost allot less, but when the engine is disassembled if its found to be heavily damaged, a rebuilt can quickly cost more than replacement.
I am pretty good working on the car, but pulling the engine and replacing with a rebuilt or new engine may be above my pay grade.
So I plan on having a shop do the work. I live in Reno, NV. there is a good shop 2hrs away in Sacramento, Ca.
So looking for some advice rebuild or replace?
08-21-21, 01:38 PM
#3
Originally Posted by all4fuun
Called the shop that did the work (I moved from the state the work was done in) and after some tests the shop is guessing that the side rotor seals are bad and cant handle the boost causing the blow by. There is no smoke coming out of the exhaust
And the boost being what's causing it sounds off too. If the boost was causing oil to blow out everywhere, that would be crank case pressure issues or turbo seal issues.
Is that shop a rotary specialist?
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gracer7-rx7 (08-24-21)
08-21-21, 02:36 PM
#4
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Mazda tends to price the whole engine to be less than the cost of a rebuild, which should make the choice pretty easy. by the time you buy all the seals, gaskets and a pair of rotor housings, you might as well get the new engine. you can look at it like once you buy the rebuild parts, Mazda will just throw the rest in, and assemble it for you for free...
that being said, oil out the PCV sounds like some tuning/setup problem
that being said, oil out the PCV sounds like some tuning/setup problem
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gracer7-rx7 (08-24-21)
08-21-21, 07:07 PM
#5
Rotary Freak
Is it a PCV though.....or a blow off? With the left side of the bay being mentioned, suggests it's a BOV with the usual mounting on the cold side of the IC.
Might be worth elaborating on what "tests" were undertaken too.......another comp?? The metric on rebuild or replace, should that be the problem, will only be discovered on disassembly.
Might be worth elaborating on what "tests" were undertaken too.......another comp?? The metric on rebuild or replace, should that be the problem, will only be discovered on disassembly.
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08-22-21, 01:50 AM
#7
Senior Member
iTrader: (2)
Some good advice here. I'm praying my engine lasts a long time on the stock twins, decent tune and low PSI. Want to enjoy it before I will inevitably just buy a brand new crate motor.
Depending how long it takes, I may just buy a crate motor now and have it ready until the current one blows. Previous owner built it himself and I have no idea of the quality of work right now.
Depending how long it takes, I may just buy a crate motor now and have it ready until the current one blows. Previous owner built it himself and I have no idea of the quality of work right now.
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08-22-21, 08:56 AM
#8
RX-7 Bad Ass
iTrader: (55)
Yeah I would make 100% sure it's the engine before going that deep.
- Check compression
- What is your oil pressure like? I'm wondering if the shop did some hacky "oil mods" that bumped your oil pressure to crazy high levels
- What is your PCV setup? Catch can?
- Single turbo or twins?
Dale
- Check compression
- What is your oil pressure like? I'm wondering if the shop did some hacky "oil mods" that bumped your oil pressure to crazy high levels
- What is your PCV setup? Catch can?
- Single turbo or twins?
Dale
08-22-21, 10:41 AM
#9
Full Member
Thread Starter
From:Billyboy
"Is it a PCV though.....or a blow off? With the left side of the bay being mentioned, suggests it's a BOV with the usual mounting on the cold side of the IC.
Might be worth elaborating on what "tests" were undertaken too.......another comp??"
Regarding the above: The BOV is on the right side of the engine if you’re sitting in the car, so it’ss the hot side, same location as stock BOV.
The test we did was to remove the oil fill cap and take a drive to see if we got any new oil in the bay, we did not.
There was a small amount of oil accumulating in the blow off valve, and probably some in the intercooler.(need to take a look at that)
In fact, even after putting the cap back on we still could not repeat the problem, but boost is low ~6-7psi, was tuned to 10-12psi at 5k-7k rpm.
We have changed the oil. The old oil heavily smelled like gas and seemed thin.
From
aleClark
- Check compression- we are going to do this
- What is your oil pressure like? I'm wondering if the shop did some hacky "oil mods" that bumped your oil pressure to crazy high levels-See below
- What is your PCV setup? Catch can?-Setting up poor mans catch can
- Single turbo or twins?-Dual 99spec stock turbos.
I dont think there is excessive oil pressure. When the original work on the engine was done, during initial tuning the oil pressure was low (40psi at 4k rpm) and the ECU shut on the engine.
Was diagnosed as a leaky internal oil seal, the shop replaced the seal and oil pump and new oil cooler (was dented), and the oil pressure went to ~90psi at 7k rpm.
I was told this is where it is supposed to be.
With the current problem the oil pressure is more like 70psi. I am thinking the gas infused oil is the reason because its thin.
Our next steps so far:
We are going to drill a hole in the oil fill cap put in a fitting and a hose to make a poor man’s catch can and see if that helps.
We are going to check compression again to see if something went bad.
We are going to get the log data from the ECU we found someone with a good reputation to help us analyze it.
Change the oil to see if pressure goes back to 90psi.
We trust the shop that did the work. They could have tunned to engine to over 400hp but like to stay on the conservative side.
Also, they tuned the power to gradualy increase upto 7k rpm and not just max boost all the time. They were pretty meticulous
about all the work they did.
"Is it a PCV though.....or a blow off? With the left side of the bay being mentioned, suggests it's a BOV with the usual mounting on the cold side of the IC.
Might be worth elaborating on what "tests" were undertaken too.......another comp??"
Regarding the above: The BOV is on the right side of the engine if you’re sitting in the car, so it’ss the hot side, same location as stock BOV.
The test we did was to remove the oil fill cap and take a drive to see if we got any new oil in the bay, we did not.
There was a small amount of oil accumulating in the blow off valve, and probably some in the intercooler.(need to take a look at that)
In fact, even after putting the cap back on we still could not repeat the problem, but boost is low ~6-7psi, was tuned to 10-12psi at 5k-7k rpm.
We have changed the oil. The old oil heavily smelled like gas and seemed thin.
From
aleClark- Check compression- we are going to do this
- What is your oil pressure like? I'm wondering if the shop did some hacky "oil mods" that bumped your oil pressure to crazy high levels-See below
- What is your PCV setup? Catch can?-Setting up poor mans catch can
- Single turbo or twins?-Dual 99spec stock turbos.
I dont think there is excessive oil pressure. When the original work on the engine was done, during initial tuning the oil pressure was low (40psi at 4k rpm) and the ECU shut on the engine.
Was diagnosed as a leaky internal oil seal, the shop replaced the seal and oil pump and new oil cooler (was dented), and the oil pressure went to ~90psi at 7k rpm.
I was told this is where it is supposed to be.
With the current problem the oil pressure is more like 70psi. I am thinking the gas infused oil is the reason because its thin.
Our next steps so far:
We are going to drill a hole in the oil fill cap put in a fitting and a hose to make a poor man’s catch can and see if that helps.
We are going to check compression again to see if something went bad.
We are going to get the log data from the ECU we found someone with a good reputation to help us analyze it.
Change the oil to see if pressure goes back to 90psi.
We trust the shop that did the work. They could have tunned to engine to over 400hp but like to stay on the conservative side.
Also, they tuned the power to gradualy increase upto 7k rpm and not just max boost all the time. They were pretty meticulous
about all the work they did.
08-22-21, 12:19 PM
#10
RX-7 Bad Ass
iTrader: (55)
Rotaries dilute oil with gas, and if the car is running richer than it should be that will be accelerated. Definitely change oil as a first step. Super thin gas-laden oil will get into weird places.
Do a search on Jaz catch can with my username, I've written it up more than once. Easy, inexpensive, and a solid setup. Don't drill your oil cap out, that's some hacky stuff there.
The root of this problem is the BOV that is on the turbo side of the engine is barfing out oil. There's only 2 ways oil can get there -
- Stock PCV hose that routes to primary turbo inlet. That's pushing oil into the primary turbo and the BOV is barfing it out.
- Turbos are bad and are leaking oil on the cold side of the turbos (compressor wheel) and it's getting in from there.
That's it. The good thing is #2 isn't common, most turbos when they go typically barf oil on the exhaust side - lots of smoke.
At this point, change oil, get a Jaz catch can, and see how you are.
As far as maybe running rich and diluting oil faster - do you know what fuel economy you get? Even a modified FD should get decent fuel economy, I get 18-19 around town and 22 highway.
Dale
Do a search on Jaz catch can with my username, I've written it up more than once. Easy, inexpensive, and a solid setup. Don't drill your oil cap out, that's some hacky stuff there.
The root of this problem is the BOV that is on the turbo side of the engine is barfing out oil. There's only 2 ways oil can get there -
- Stock PCV hose that routes to primary turbo inlet. That's pushing oil into the primary turbo and the BOV is barfing it out.
- Turbos are bad and are leaking oil on the cold side of the turbos (compressor wheel) and it's getting in from there.
That's it. The good thing is #2 isn't common, most turbos when they go typically barf oil on the exhaust side - lots of smoke.
At this point, change oil, get a Jaz catch can, and see how you are.
As far as maybe running rich and diluting oil faster - do you know what fuel economy you get? Even a modified FD should get decent fuel economy, I get 18-19 around town and 22 highway.
Dale
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08-22-21, 07:13 PM
#11
Rotary Freak
There is a third way for oil to end up where it has - oil injector failure. It will only coat the entire tract, but wouldn't expect "half the engine bay" to be wet......especially on the opposite side. I'd be degreasing thoroughly to see if anything is amiss.
Be interesting to see if the haltech log turns up anything, normally intermittent boost is the paradigm on sequential twins, a consistent 7lb from 12lb is a bit out of the ordinary.
Be interesting to see if the haltech log turns up anything, normally intermittent boost is the paradigm on sequential twins, a consistent 7lb from 12lb is a bit out of the ordinary.
08-23-21, 09:45 AM
#12
Full Member
Thread Starter
Thanks everybody for the help.
We changed the oil, the oil pressure went from ~70pis with old diluted oil to ~90psi with new oil ~3000rpm to ~4000rpm. This is where it was before all this started happening.
We will check out the Jaz catch can as a premenant solution, but drilled the old oil cap already (have a new one to replace it with)
To answer some questions:
The gas mileage is not very good, we estimate about 250 miles per tank. I have not done miles/gallon math yet.
DaleClark: Could you explin a bit more about waht we should be looking for to see if the turbos are bad. Before we left So. Cal the turbos barfed out oil 1 time. We went back to the shop and found the hose from the oil fill neck to PCV was kinked. Since then not much oil has come out of the turnos, we shorted that hose a bit to prevent it from kinking.
Billyboy:I had been thinking maybe a bad injector as well. We plan to check the compression today and I am think if there is an overactive injector we will get gas out of the spark plus hole when checking. Do you know if thats what would find? Also all the emisssion stuff was removed, so our engine is dual turbo no sequential.
We changed the oil, the oil pressure went from ~70pis with old diluted oil to ~90psi with new oil ~3000rpm to ~4000rpm. This is where it was before all this started happening.
We will check out the Jaz catch can as a premenant solution, but drilled the old oil cap already (have a new one to replace it with)
To answer some questions:
The gas mileage is not very good, we estimate about 250 miles per tank. I have not done miles/gallon math yet.
DaleClark: Could you explin a bit more about waht we should be looking for to see if the turbos are bad. Before we left So. Cal the turbos barfed out oil 1 time. We went back to the shop and found the hose from the oil fill neck to PCV was kinked. Since then not much oil has come out of the turnos, we shorted that hose a bit to prevent it from kinking.
Billyboy:I had been thinking maybe a bad injector as well. We plan to check the compression today and I am think if there is an overactive injector we will get gas out of the spark plus hole when checking. Do you know if thats what would find? Also all the emisssion stuff was removed, so our engine is dual turbo no sequential.
08-23-21, 10:12 AM
#13
Full Member
Thread Starter
I looked at the catch can write up
All I need to do is run the 2 nipples on the oil fill neck to the catch can?
Dont need the PCV line thats currently there or anything to/from the turbo?
The install pics I found are hard to make out exactly what I am looking at.
All I need to do is run the 2 nipples on the oil fill neck to the catch can?
Dont need the PCV line thats currently there or anything to/from the turbo?
The install pics I found are hard to make out exactly what I am looking at.
08-23-21, 03:19 PM
#14
RX-7 Bad Ass
iTrader: (55)
On the catch can, yes, just run 2 lines to the 2 nipples on the oil fill neck.
The hose that goes now from the oil fill neck to the upper intake manifold that has the larger PCV valve in it, eliminate that and cap the nipple on the UIM. Use a GOOD cap and clamp it on.
The other nipple on the oil fill neck goes to the primary turbo inlet, again just cap that.
If you get that setup done and are still getting oil on the intake tract, that's when I'd suspect turbos.
Dale
The hose that goes now from the oil fill neck to the upper intake manifold that has the larger PCV valve in it, eliminate that and cap the nipple on the UIM. Use a GOOD cap and clamp it on.
The other nipple on the oil fill neck goes to the primary turbo inlet, again just cap that.
If you get that setup done and are still getting oil on the intake tract, that's when I'd suspect turbos.
Dale
08-23-21, 05:51 PM
#15
Full Member
Thread Starter
We checked the compression today.
I think you would call this pretty low, we get pulses to ~70psi-75psi. Its even across all 4 test points.
I think good is above 90psi, right?
Looking for anything we may have done wrong that is causing out reading to be low
How we did it:We used a regular compression gauge, and removed the schrader value.
We did the compression test with the engine cold, may should have been warm?
We read the pulses from 0-70psi.
Odd thing is before we had the build done the compression was 85-90psi, there is less than 1000miles run on the engine since the build.
I think you would call this pretty low, we get pulses to ~70psi-75psi. Its even across all 4 test points.
I think good is above 90psi, right?
Looking for anything we may have done wrong that is causing out reading to be low
How we did it:We used a regular compression gauge, and removed the schrader value.
We did the compression test with the engine cold, may should have been warm?
We read the pulses from 0-70psi.
Odd thing is before we had the build done the compression was 85-90psi, there is less than 1000miles run on the engine since the build.
Last edited by all4fuun; 08-23-21 at 10:22 PM.
08-23-21, 10:19 PM
#16
Full Member
Thread Starter
Dale
I ordered the Jax catch can.
For nipple that runs from the oil fill neck to the primary turbo inlet, its now going to that catch can.
So I just can the cap the nipple on the turbo inlet where the hose was running to right, just want to double check.
Also, is it possbile for you to post or point me to a post of where you placed the catch can.
I am pretty sure I know based on your description, but want to be sure.
I ordered the Jax catch can.
For nipple that runs from the oil fill neck to the primary turbo inlet, its now going to that catch can.
So I just can the cap the nipple on the turbo inlet where the hose was running to right, just want to double check.
Also, is it possbile for you to post or point me to a post of where you placed the catch can.
I am pretty sure I know based on your description, but want to be sure.
08-24-21, 10:39 AM
#17
RX-7 Bad Ass
iTrader: (55)
I may have posted pics at some point. I made a simple bracket and mounted it to the left stud that holds the brake master cylinder to the brake booster. Good room in that area and the hose run was relatively short.
Yes, you can cap that nipple on the primary turbo inlet.
Compression test is hard to say anything on. A piston tester is just good for seeing if you have a blown seal - you can see the pulses. 1 high pulse and 2 lows are a broken apex seal, 2 highs and a low is a side seal or corner seal problem. To really get a proper idea of the health of the engine you have to use a rotary compression tester - https://www.rotarycompressiontester.com - that's the best one out there for a great price that gives solid results. It also corrects for speed which is key - tests have to be compared at 250rpm. But, at least you know you don't have a bad apex seal or something and those numbers aren't super low.
Dale
Yes, you can cap that nipple on the primary turbo inlet.
Compression test is hard to say anything on. A piston tester is just good for seeing if you have a blown seal - you can see the pulses. 1 high pulse and 2 lows are a broken apex seal, 2 highs and a low is a side seal or corner seal problem. To really get a proper idea of the health of the engine you have to use a rotary compression tester - https://www.rotarycompressiontester.com - that's the best one out there for a great price that gives solid results. It also corrects for speed which is key - tests have to be compared at 250rpm. But, at least you know you don't have a bad apex seal or something and those numbers aren't super low.
Dale
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gracer7-rx7 (08-24-21)
08-24-21, 11:22 AM
#19
Full Member
Thread Starter
DaleClark
Well thats some good news. I watched the videos we took of the compression test we took and its just single pules.
I will get that tester and run it again.
Net thing we are also going to do is the the log data out of the Haltech ECU.
Thanks allot for your help.
fandamonky:
I dont think the rotary shop used a piston compression tester. I dont really know what they used, but
we use one cause its all we had and I didnt know we needed a special rotary compression tester.
Well thats some good news. I watched the videos we took of the compression test we took and its just single pules.
I will get that tester and run it again.
Net thing we are also going to do is the the log data out of the Haltech ECU.
Thanks allot for your help.
fandamonky:
I dont think the rotary shop used a piston compression tester. I dont really know what they used, but
we use one cause its all we had and I didnt know we needed a special rotary compression tester.
Last edited by all4fuun; 08-24-21 at 11:25 AM.
08-26-21, 11:34 PM
#22
Full Member
Thread Starter
Update
We waiting for the rotary compression tester to arrive, hopefully this weekend.
Waiting for the catch can to arrive, hopefully Monday.
We got the log data out of the Haltech and are sendng it to a shop in Sacramento who offered to analyze it for us.
We also had the tunner login to the ecu to look at the logged data and check other things.
He saw that the boost is was down from what he tunned to. Which we knew.
It was tunned to 12psi, shows 6psi max. He thought maybe we are running on 1 turbo
Other than that all the settings looked fine, specifically it was not running rich, AFR was 14.4.
When we told him how bad the oil smells like gas he said he had seen cases where an injector got a a microscopic amount dirt in it
and is ever so slightly stuck on. I dont think is our case cause it was not running rich. We have a pretty decent after market fuel filter on.
->The rats nest has all been removed with the work we had done
-> and with it sequential turbos, but we still have the stock dual turbos on.
He recommended we check the turbines on the turbos, which we did today.
They spin fine and no lateral play. So they seem good.
But they had oil in them.
The catch can may help that right?
Is there anythng else we should check while we have access?
We waiting for the rotary compression tester to arrive, hopefully this weekend.
Waiting for the catch can to arrive, hopefully Monday.
We got the log data out of the Haltech and are sendng it to a shop in Sacramento who offered to analyze it for us.
We also had the tunner login to the ecu to look at the logged data and check other things.
He saw that the boost is was down from what he tunned to. Which we knew.
It was tunned to 12psi, shows 6psi max. He thought maybe we are running on 1 turbo
Other than that all the settings looked fine, specifically it was not running rich, AFR was 14.4.
When we told him how bad the oil smells like gas he said he had seen cases where an injector got a a microscopic amount dirt in it
and is ever so slightly stuck on. I dont think is our case cause it was not running rich. We have a pretty decent after market fuel filter on.
->The rats nest has all been removed with the work we had done
-> and with it sequential turbos, but we still have the stock dual turbos on.
He recommended we check the turbines on the turbos, which we did today.
They spin fine and no lateral play. So they seem good.
But they had oil in them.
The catch can may help that right?
Is there anythng else we should check while we have access?
Last edited by all4fuun; 08-26-21 at 11:42 PM. Reason: add more info